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GREAT SPIRAL NEBULA IN ANDROMEDA 





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CURIOSITIES 


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OF THE SKY 


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BY 


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GARRETT P. SERVISS 


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AUTHOR OF 


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"astronomy with the naked eye" 


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WITH MANY ILLUSTRATIONS FROM 


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NEW YORK AND LONDON 


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HARPER & BROTHERS PUBLISHERS 


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MCMIX 


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Copyright, 1909, by Harper & Brothers. 



Aii rights reserved. 
Published November, igog. 



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CONTENTS 
I 

THE WINDOWS OF ABSOLUTE NIGHT 

On the edges of the universe — The mystery of the " Coal-sacks" — 
Description of the great "Coal-sack" in the "Southern Cross" 
— Its effect upon the imagination — The "Coal-sack" in Cygnus 
— Photographic discovery of apparent apertures in the Milky 
Way — Strange lanes among the stars — Professor Barnard's 
theory of "Dark Nebulae" — The problem of the extinction 
of light in space — If the " Coal-sacks" are openings in the walls 
of the universe, what lies beyond ? — Inconceivability of an 
end to space — The universe not a Crusoe lost in immensity — 
Reasons for thinking that other universes exist — What is their 
probable appearance ? — Will any of them ever be seen from 
our starry system ? — Does the luminiferous ether extend 
throughout infinite space? Page i 

II 

STAR-CLOUDS, STAR-CLUSTERS, AND STAR-STREAMS 

The Milky Way the most stupendous of all astronomical phe- 
nomena — The strange ground-plan of the universe — A chaplet 
of a hundred million suns — An extraordinary speculation con- 
cerning the nature of the Galaxy — Professor Comstock's "star- 
plough" — The wonderful details of the Milky Way — Distinc- 
tion between star-clouds, star-swarms, and star-clusters — The 
mystery of the globular star-clusters — The " Great Cluster in 
Hercules" and the still richer one in Centaurus — How did the 
stars in dense clusters come together ? — The startling idea of an 
explosion — The wonderful association of stars and nebulse 
in the Pleiades — Nebulous "rail fences" with strange banks 
of stars arrayed along them , . Page 17 

V 



CONTENTS 

III 

STELLAR MIGRATIONS 

The paradox of the "fixed stars" — All is motion in the universe — 
Extraordinary speed of some "runaway stars" — The fearful 
momentum of Arcturus — What is to become of stars whose 
motion is so swift that the attractions of the universe cannot 
govern them? — Stars travelling in groups — The motion of the 
solar system — Whence have we come, and whither do we go ? 
— Enormous spaces that the earth has traversed during the 
geologic ages — Curious thoughts suggested by this stupendous 
voyage — Shall we eventually join the Milky Way? — The ex- 
traordinary theory of a double drift of the stars — Is the stellar 
system divided into two opposed streams? — Stars moving like 
snow-flakes driven before interpenetrating winds . . Page 39 

IV 

THE PASSING OF THE CONSTELLATIONS 

How time affects the blazonry of the heavens — The constellations 
and human tradition — The most lasting records of men's 
thoughts — The constellations and religion — American tradi- 
tions — The wonderful impression made by Greek tradition as 
preserved in the stars — The effects of the stellar motions in 
difforming the constellations — When the "Great Dipper" 
will no longer hold water — Curious results of star-drift in the 
"Northern Crown" — The Hyades drifting apart — Famous 
star figures, full of poetic suggestion, which cannot last — Orion, 
the " Mighty Hunter," stands almost unchanged, but his "belt" 
is falling to pieces — The curious fate that attends the beautiful 
"Southern Cross" — Future mythologies must invent new 
constellations — The sun among the constellations seen from 
distant space Page 53 

V 

CONFLAGRATIONS IN THE HEAVENS 

The burning up of the earth would be a catastrophe invisible 
from stellar space — Yet many great outbursts of light have 
appeared to us among the stars — The phenomena of new or 
temporary stars — The famous star of Tycho — The legend that 

vi 



CONTENTS 

it was a reappearance of the "Star of Bethlehem" — Kepler's 
starv and other fiery outbursts — The great new star of 1901, 
"Nova Persei," and the light it has thrown on such phenomena 
— Extraordinary theories based upon it — Was it the result of a 
collision ? — How suns may be a source of danger to each other 
without coming into actual collision — The theory of an en- 
counter between a star and a "dark nebula" — Suggestion of 
the "running down" of planets by an invading star — Janssen's 
theory of explosive chemical action — How temporary stars 
appear to run through the stages of stellar history in a few 
months — Significance of their changes of color . . Page 68 

VI 
EXPLOSIVE AND WHIRLING NEBULAE 

Professor Keeler's surprising discovery that most of the nebulse 
are spiral in form — The effect of this discovery on Laplace's 
Nebular H5rpothesis — Immense variety of the spiral forms — 
Is Laplace's hypothesis still applicable, with modifications, to 
our particular system? — Suggestive forms of "rings" and 
" planetary " nebulae — The marvels revealed by photography 
in Lord Rosse's "Whirlpool," and the amazing spectacle pre- 
sented by a spiral nebula in TrianguUim — Other strange 
forms — The wonderful Andromeda Nebula — The mystery of 
the "white" nebulae — The chaotic gaseous nebula in Orion — 
Suggestive arrangement accompanying stars — Are these nebulae 
the birthplaces of star-clusters? — The new " Planetesimal Hy- 
pothesis," and the astonishing view of the origin of solar sys- 
tems that it offers — Do we yet know the real truth ? . Page 88 

VII 
THE BANNERS OF THE SUN 

The wonderful surroundings of the sun that only an eclipse re- 
veals — The dramatic story of the first scientific observation of 
the corona and the prominences of the sun — The corona of 
1900 and 1905 — The curved rays about the solar poles resem- 
bling the lines of force of a magnet — Solar magnetic influence 
upon the earth — The phenomena of the eruptive prominences 
— Does the sun hurl forth masses of matter that reach the 
planets? — Connection of the prominences and the corona with 
sun-spots — The remarkable results of the "pressure of light" — ■ 
The sun-spot period and "magnetic storms" — The sun a 

vii 



CONTENTS 

variable star — How its light is partially cut off by absorbing 
\apors — Once it probably shone more brilliantly than it does 
at the present time Page 113 

VIII 
THE ZODIACAL LIGHT MYSTERY 

The ghostly presence that towers above the sunken sun — The 
light varies in appearance with the seasons — How it looks in 
the tropics and upon the equator — Humboldt's observations — 
The Zodiacal Light in 1909 — The writer's observations — The 
curious "Gegenschein" — Professor Barnard's observations — The 
Rev. Mr. Jones' round the world studies of the Zodiacal Light 
— The extraordinary theory of Arrhenius — Once more the 
pressure of light — How negatively charged corpuscles driven 
from the sun are conceived to envelop the earth and produce 
the appearance of the Zodiacal Light — The theories of coronal 
extension and of clouds of meteors — Why an airless planet 
cannot have comets' tails as the earth is supposed to 
have Page 131 

IX 

MARVELS OF THE AURORA 

An amazing spectacle that recalled pictures of "The Day of 
Judgment" — The aurora of 1882, and the strange upright 
beam that appeared stalking across the sky — Aurorae in the 
Arctic and Antarctic regions — Their connection with the 
magnetic poles — The earth as a great magnet — Astonishing 
phenomenon observed in 1859 — Outbursts on the sun followed 
by extraordinary auroral displays and magnetic storms on the 
earth — Lord Kelvin's objection, and the answer to it — Proofs 
of the intimate connection between solar outbreaks and terres- 
trial disturbances — Another application of the theory of 
Arrhenius — Negative particles shot from the sun supposed to 
electrify the earth's atmosphere and thus to produce the 
play of the auroral lights — Curious confirmations of the 
theory Page 144 

X 

STRANGE ADVENTURES OP COMETS 

How the fears and superstitions of ancient times have been suc- 
ceeded by scientific study of comets — An account of the 

viii 



CONTENTS 

characteristic phenomena of a comet — Science itself has dis- 
covered mysteries — How the nuclei and tails of comets are 
developed — The chemical constituents of comets — Remarkable 
comets of the nineteenth century — The monster of space that 
looked at us afar off in 1729 — The great comet of 181 1, and 
its enormous tail — In 1843 ^ comet was visible in broad day 
beside the sun — The beautiful comet of 1858, and its supposed 
connection with the wine crop — Astonishing association of 
the comets of 1843, 1880, and 1882 — Three pieces of one orig- 
inal mass — The disintegration of the head of the comet of 
1882 — Professor Forbes' theory that these comets were split 
up by the action of a yet undiscovered planet beyond Neptune — 
Strange adventures of Lexell's comet — Arrhenius' theory of 
the origin of comets' tails — Driven off by the pressure of light — 
Jupiter as the great comet-catcher — Do comets ever come into 
the solar system from interstellar space, or are they originally 
carried along in the same "current" that bears onward the sun 
and the planets? . . - Page 165 

XI 

METEORS, FIRE-BALLS, AND METEORITES 

The terrorizing spectacle of 1833 and its connection with a dis- 
integrated comet — The "umbrella of fire" and the light that 
it cast on the meaning of the amazing display — Olmstead's and 
Schiaparelli's investigations — Meteor-swarms travel in the 
tracks of comets — The tragic fate of Biela's comet — Why the 
November spectacle failed in 1899 — The distinction between 
meteors and meteorites — Stone meteorites and iron meteorites 
— Former incredulity of men of science concerning stones fall- 
ing from the sky — Shov/ers of stones — Famous meteorites of 
ancient times — Nickel-iron from the sky — Diamonds in me- 
teorites — Do such bodies come from the sun or the stars, or 
have they been shot out from lunar volcanoes ? — The mystery 
of Coon Butte — Was the crater in Arizona made by a falling 
meteorite? Page 186 

XII 

THE WRECKING OF THE MOON 

A "fossil world" in the sky — Unique character of the lunar 
scenery — The story of disaster that the moon carries sculptured 

.ix 



CONTENTS 

on its face — Gigantic size of the craters of the moon — How 
they differ from the volcanic craters of the earth — Some strik- 
ing comparisons of magnitude — How the slight force of lunar 
gravity may account for the gigantic dimensions of the craters 
— The theory that they may have been formed by meteoric 
impact — The question of former life on the moon — The uni- 
versality of the destruction wrought by the volcanoes — The 
puzzle of the ancient sea beds — Were they once floods of molten 
lava? — Mr, Ritchey's wonderful photographs and their revela- 
tions — Suggestions of a doiible tragedy in the career of the 
lunar world — Ruin beneath ruin recalling the strata of buried 
cities in the mound of ancient Troy Page 213 

XIII 
THE GREAT MARS PROBLEM 

Life not ubiquitous, though probably present in all quarters of 
the universe — The life question in the solar system — Why Mars 
has been selected as the most probable abode of life among 
the other planets — The principal facts known about Mars — 
Its singular resemblances to the earth, and its no less remark- 
able differences from our planet — The discoveries of Schiaparelli 
and Lowell — The problematical "canals," their peculiarities, 
and the interpretation that has been put upon them — Mars 
a half-dried-up world — The wonderful struggle to retain life 
which is ascribed to its inhabitants — Their possibly gigantic 
size, and the reasons which have been given for thinking that 
they may be more advanced than we are — Mr. Lowell's theory 
of life on Mars — Public works that put the utmost achieve- 
ments of man to shame — Objections, and the answers to 
them Page 235 

XIV 
THE RIDDLE OF THE ASTEROIDS 

A ring of little worlds where astronomers expected to find a single 
large one — Olbers' startling hypothesis of a planetery explosion 
— Measures of the four largest asteroids — The objections to the 
explosion hypothesis, and the support which it seems to derive 
from the probable abnormal shapes of Eros and others — 
The theory of a series of explosions — How could a world ex- 
plode? — Evidences of explosive forces in nature — The ex- 

X 



CONTENTS 

traordinary ideas of Doctor Le Bon concerning the results of 
atomic disintegration — The phenomena of the radium group of 
elements appealed to in support of the hypothesis that worlds 
may blow up when they have grown very old — This, says 
Doctor Le Bon, may represent the most general ending of the 
bodies composing the universe Page 252 

Index 263 



ILLUSTRATIONS 

GREAT SPIRAL NEBULA IN ANDROMEDA Frontispiece 

THE MILKY WAY Facingp. 4 

STAR-CLUSTER IN HERCULES " 26 

GREAT SOUTHERN STAR-CLUSTER, OMEGA CENTAURI . " 30 

THE PLEIADES , " 34 

THE "great dipper" Page 58 

CASSIOPEIA , " 60 

THE "northern CROWN " " 63 

THE "southern CROSS " " 6e 

CHART SHOWING LOCATION OF TYCHO's STAR, I 572, AND 

NOVA PERSEI OF 1901 Facingp. 70 

NOVA PERSEI, WITH ITS NEBULAR RINGS .... " 80 

LORD ROSSE's NEBULA " 88 

WONDERFUL SPIRAL IN TRIANGULUM " 92 

SPIRAL IN URSA MAJOR . . . " 96 

NEBULA IN CETUS " loO 

THE ORION NEBULA " 104 

THE CORONA " 114 

A SOLAR "prominence" " 120 

AURORAL BEAMS SEEN IN ENGLAND " 144 

AURORAL ARCHES OF AN ELLIPTIC FORM SEEN IN THE 

ARCTIC REGIONS " I48 

AURORAL CURTAIN SEEN IN SCANDINAVIA .... " 154 

AURORAL ARCHES SEEN IN SCANDINAVIA " 160 

swift's COMET *' 166 

xiii 



ILLUSTRATIONS 



DANIELS' COMET Facingp. iy6 

brooks' comet " i8o 

CURIOUS FORMS OF METEORITE TRAINS ..... " l88 

SECTION OF THE ATMOSPHERE UP TO lOO KILOMETERS . " 192 

A METEOR PHOTOGRAPHED IN FLIGHT " 198 

LOOKING ACROSS COON BUTTE CRATER FROM NORTHERN 

RIM . " 204 

TRAIL ON SOUTH SIDE, COON BUTTE CRATER ... " 2o8 

THE CRATERS CLAVIUS, LONGOMONTANUS, TYCHO, ETC. ** 2l6 

WESTERN PART OF THE MARE SERENITATIS .... ** 222 

MARE TRANQUILITATIS AND SURROUNDINGS .... " 226 

LUNAR CRATER THEOPHILUS AND SURROUNDING REGION ** 230 

MARE CRISIUM " 234 

SCHIAPARELLI'S CHART OF MARS, SHOWING THE SYSTEM 

OF SO-CALLED CANALS ** 244 



PREFACE 



WHAT Froude says of history is true also of 
astronomy: it is the most impressive where it 
transcends explanation. It is not the mathematics 
of astronomy, but the wonder and the mystery that 
seize upon the imagination. The calculation of an 
eclipse owes all its prestige to the sublimity of its 
data ; the operation, in itself, requires no more mental 
effort than the preparation of a railway time-table. 

The dominion which astronomy has always held 
over the minds of men is akin to that of poetry ; when 
the former becomes merely instructive and the latter 
purely didactic, both lose their power over the imag- 
ination. Astronomy is known as the oldest of the 
sciences, and it will be the longest-lived because it will 
always have arcana that have not been penetrated. 

Some of the things described in this book are little 
known to che average reader, while others are well 
known; but all possess the fascination of whatever is 
strange, marvellous, obscure, or mysterious — magni- 
fied, in this case, by the portentous scale of the 
phenomena. 

The idea of the author is to tell about these things 
in plain language, but with as much scientific accuracy 

XV 



PREFACE 

as plain language will permit, showing the wonder 
that is in them without getting away from the facts. 
Most of them have hitherto been discussed only in 
technical form, and in treatises that the general 
public seldom sees and never reads. 

Among the topics touched upon are: The strange 
unfixedness of the ''fixed stars," the vast migrations 
of the suns and worlds constituting the universe; 
The slow passing out of existence of those collocations 
of stars which for thousands of years have formed 
famous "constellations," preserving the memory of 
mythological heroes and heroines, and perhaps of 
otherwise unrecorded history; The tendency of stars 
to assemble in immense clouds, swarms, and clusters; 
The existence in some of the richest regions of the 
universe of absolutely black, starless gaps, deeps, 
or holes, as if one were looking out of a window into 
the murkiest night; The marvellous phenomenon of 
new, or temporary, stars, which appear as suddenly 
as conflagrations, and often turn into something else 
as eccentric as themselves; The amazing forms of the 
"whirlpool," "spiral," "pin wheel," and "lace," or 
"tress," nebula; The strange surroundings of the sun, 
only seen in particular circumstances, but evidently 
playing a constant part in the daily phenomena of 
the solar system; The mystery of the Zodiacal Light 
and the Gegenschein; The extraordinary transforma- 
tions undergone by comets and their tails ; The prodi- 
gies of meteorites and masses of stone and metal 
fallen from the sky; The cataclysms that have 
wrecked the moon; The problem of life and intelli- 
gence on the planet Mars; The problematical origin 

xvi 



PREFACE 

and fate of the asteroids; and The strange phenom- 
ena of the auroral Hghts. 

An attempt has been made to develop these topics 
in an orderly way, showing their connection, so that 
the reader may obtain a broad general view of the 
chief mysteries and problems of astronomy, and an 
idea of the immense field of discovery which still lies, 
almost unexplored, before it. 



CURIOSITIES OF THE SKY 



CURIOSITIES OF THE SKY 



THE WINDOWS OF ABSOLUTE NIGHT 

TO most minds mystery is more fascinating than 
science. But when science itself leads straight 
up to the 'borders of mystery and there comes to a 
dead stop, saying, "At present I can no longer see 
my way," the force of the charm is redoubled. On 
the other hand, the illimitable is no less potent in 
mystery than the invisible, whence the dramatic 
effect of Keats' ''stout Cortez" staring at the bound- 
less Pacific while all his men look at each other with a 
wild surmise, ''silent upon a peak in Darien." It is 
with similar feelings that the astronomer regards 
certain places where from the peaks of the universe 
his vision seems to range out into endless empty 
space. He sees there the shore of his little isthmus, 
and, beyond, unexplored immensity. 

The name, "coal -sacks," given to these strange 
voids is hardly descriptive. Rather they produce 
upon the mind the effect of blank windows in a lonely 
house on a pitch-dark night, which, when looked at 
from the brilliant interior, become appalling in their 



CURIOSITIES OF THE SKY 

rayless murk. Infinity seems to acquire a new mean- 
ing in the presence of these black openings in the sky, 
for as one continues to gaze it loses its purely meta- 
physical quality and becomes a kind of entity, like 
the ocean. The observer is conscious that he can 
actually see the beginning of its ebon depths, in 
which the visible universe appears to float like an en- 
chanted island, resplendent within with lights and 
life and gorgeous spectacles, and encircled with 
screens of crowded stars, but with its dazzling vistas 
ending at the fathomless sea of pure darkness which 
encloses all. 

The Galaxy, or Milky Way, surrounds the borders 
of our island in space like a stellar garland, and when 
openings appear in it they are, by contrast, far more 
impressive than the general darkness of the inter- 
stellar expanse seen in other directions. Yet even 
that expanse is not every^v^^here equally dark, for it 
contains gloomy deeps discernible with careful watch- 
ing. Here, too, contrast plays an important part, 
though less striking than within the galactic region. 
Some of Sir William Herschel's observations appear 
to indicate an association between these tenebrious 
spots and neighboring star-clouds and nebulae. It is 
an illuminating bit of astronomical history that when 
he was sweeping the then virgin heavens with his great 
telescopes he was accustomed to say to his sister who, 
note-book in hand, waited at his side to take down 
his words, fresh with the inspiration of discovery: 
' ' Prepare to write ; the nebula are coming ; here space 
is vacant." 

The most famous of the "coal-sacks," and the first 



WINDOWS OF ABSOLUTE NIGHT 

to be brought to general attention before astronomers 
had awakened to the significance of such things, lies 
adjacent to the "Southern Cross," and is truly an 
amazing phenon^enon. It is not alone the conspicu- 
ousness of this celestial vacancy, opening suddenly in 
the midst of one of the richest parts of the Galaxy, 
that has given it its fame, but quite as much the super- 
stitious awe with which it was regarded by the early 
explorers of the South Seas. To them, as well as to 
those who listened in wrapt wonder to their tales, the 
''Coal-sack" seemed to possess some occult connection 
with the mystic "Cross." In the eyes of the sailors 
it was not a vacancy so much as a sable reality in the 
sky, and as, shuddering, they stared at it, they piously 
crossed themselves. It was another of the magical 
wonders of the unknown South, and as such it formed 
the basis of many a "wild surmise" and many a sea- 
dog's yam. Scientific investigation has not diminished 
its prestige, and to-day no traveller in the southern 
hemisphere is indifferent to its fascinating strangeness, 
while some find it the most impressive spectacle of the 
antarctic heavens. 

All around, up to the very edge of the yawning gap, 
the sheen of the Milky Way is surpassingly glorious; 
but there, as if in obedience to an almighty edict, 
ever^^thing vanishes. A single faint star is visible 
within the opening, producing a curious effect upon the 
sensitive spectator, like the sight of a tiny islet in the 
midst of a black, motionless, waveless tarn. The di- 
mensions of the lagoon of darkness, which is oval or 
pear-shaped, are eight degrees by five, so that it oc- 
cupies a space in the sky about one hundred and thirty 

3 



CURIOSITIES OF THE SKY 

times greater than the area of the full moon. It 
attracts attention as soon as the eye is directed toward 
the quarter where it exists, and by virtue of the rarity 
of such phenomena it appears a far greater wonder 
than the drifts of stars that are heaped around it. 
Now that obser\^atories are multiplying in the southern 
hemisphere, the great austral *' Coal -sack'' will, no 
doubt, receive attention proportioned to its importance 
as one of the most significant features of the sky. 
Already at the Sydney Observatory photographs have 
shown that the southern portion of this Dead Sea of 
Space is not quite ''bottomless," although its northern 
part defies the longest sounding lines of the astronomer. 

There is a similar, but less perfect, "coal-sack" in 
the northern hemisphere, in the constellation of 
"The Swan," which, strange to say, also contains a 
well-marked figure of a cross outlined by stars. This 
gap lies near the top of the cross-shaped figure. It is 
best seen by averted vision, which brings out the con- 
trast with the Milky Way, which is quite brilliant 
around it. It does not, however, exercise the same 
weird attraction upon the eye as the southern "Coal- 
sack," for instead of looking like an absolute void in 
the sky, it rather appears as if a canopy of dark gauze 
had been drawn over the stars. We shall see the 
possible significance of this appearance later. 

Just above the southern horizon of our northern 
middle latitudes, in summer, where the Milk^^ Way 
breaks up into vast sheets of nebulous luminosity, 
lying over and between the constellations Scorpio and 
Sagittarius, there is a remarkable assemblage of 
"coal-sacks," though none is of great size. One of 

4 




THE MILKY WAY. 



REGION NEAR M 8. PHOTOGRAPHED BY 
PROFESSOR BARNARD 



WINDOWS OF ABSOLUTE NIGHT 

them, near a conspicuous star - cluster in Scorpio, 
80 M, is interesting for having been the first of these 
strange objects noted by Herschel. Probably it was 
its nearness to 80 M which suggested to his mind the 
apparent connection of such vacancies with star- 
clusters which we have already mentioned. 

But the most marvellous of the "coal-sacks" are 
those that have been found by photography in 
Sagittarius. One of Barnard's earliest and most 
excellent photographs includes two of them, both in 
the star-cluster 8 M. The larger, which is roughly 
rectangular in outline, contains one little star, and its 
smaller neighbor is lune-shaped — surely a most singu- 
lar form for such an object. Both are associated with 
curious dark lanes running through the clustered 
stars like trails in the woods. Along the borders of 
these lanes the stars are ranked in parallel rows, and 
what may be called the bottoms of the lanes are not 
entirely dark, but pebbled with faint stellar points. 
One of them which skirts the two dark gaps and 
traverses the cluster along its greatest diameter is 
edged with lines of stars, recalling the alignment of the 
trees bordering a French highway. This road of stars 
cannot be less than many billions of miles in length! 

All about the cluster the bed of the Galaxy is 
strangely disturbed, and in places nearly denuded, 
as if its contents had been raked away to form the 
immense stack and the smaller accumulations of 
stars around it. The well-known ''Trifid Nebula" 
is also included in the field of the photograph, which 
covers a truly marvellous region, so intricate in its 
mingling of nebulae, star-clusters, star-swarms, star- 

7 



CURIOSITIES OF THE SKY 

streams, and dark vacancies that no description can 
do it justice. Yet, chaotic as it appears, there is an 
unmistakable suggestion of unity about it, impressing 
the beholder with the idea that all the different parts 
are in some way connected, and have not been for- 
tuitously thrown together. Miss Agnes M. Gierke 
made the striking remark that the dusky lanes in 
8 M are exemplified on the largest scale in the great 
rift dividing the Milky Way, from Cygnus in the north- 
ern hemisphere all the way to the "Cross" in the 
southern. Similar lanes are found in many other 
clusters, and they are generally associated with flank- 
ing rows of stars, resembling in their arrangement the 
thick-set houses and villas along the roadways that 
traverse the approaches to a great city. 

But to return to the black gaps. Are they really 
windows in the star- walls of the universe? Some of 
them look rather as if they had been made by a shell 
fired through a luminous target, allowing the eye to 
range through the hole into void space beyond. If 
science is discreetly silent about these things, what 
can the more venturesome and less responsible imag- 
ination suggest? Would a huge "runaway sun," like 
Arcturus, for instance, make such an opening if it 
should pass like a projectile through the Milky Way? 
It is at least a stimulating inquiry. Being probably 
many thousands of times more massive than the 
galactic stars, such a stellar missile would not be 
stopped by them, though its direction of flight might 
be altered. It would drag the small stars lying close 
to its course out of their spheres, but the ultimate 
tendency of its attraction would be to sweep them 

8 



WINDOWS OF ABSOLUTE NIGHT 

round in its wake, thus producing rather a star-swarm 
than a vacancy. Those that were very close to it 
might be swept away in its rush and become its sat- 
ellites, careering away with it in its flight into outer 
space ; but those that were farther off, and they would, 
of course, greatly outnumber the near ones, would 
tend inward from all sides toward the line of flight, 
as dust and leaves collect behind a speeding motor 
(though the forces operating would be different) , and 
would fill up the hole, if hole there were. A swarm 
thus collected should be rounded in outline and bor- 
dered with a relatively barren ring from which the 
stars had been ''sucked" away. In a general sense 
the 8 M cluster answers to this description, but even 
if we undertook to account for its existence by a sup- 
position like the above, the black gaps would remain 
unexplained, unless one could make a further draft 
on the imagination and suggest that the stars had been 
thrown into a vast eddy, or system of eddies, whose 
vortices appear as dark holes. Only a maelstrom- 
like motion could keep such a funnel open, for with- 
out regard to the impulse derived from the projectile, 
the proper motions of the stars themselves would 
tend to fill it. Perhaps some other cause of the 
whirling motion may be found. As we shall see 
when we come to the spiral nebulae, gyratory move- 
ments are exceedingly prevalent throughout the 
universe, and the structure of the Milky Way is every- 
where suggestive of them. But this is hazardous 
sport even for the imagination — to play with suns as 
if they were but thistle-down in the wind or corks in 
a mill-race. 



CURIOSITIES OF THE SKY 

Another question arises: What is the thickness of 
the hedge of stars through which the holes penetrate ? 
Is the depth of the openings proportionate to their 
width? In other words, is the Milky Way round in 
section like a rope, or flat and thin like a ribbon? 
The answer is not obvious, for we have little or no 
information concerning the relative distances of the 
faint galactic stars. It would be easier, certainly, to 
conceive of openings in a thin belt than in a massive 
ring, for in the first case they would resemble mere rifts 
and breaks, while in the second they would be like wells 
or bore-holes. Then, too, the fact that the Milky Way 
is not a continuous body but is made up of stars whose 
actual distances apart is great, offers another quan- 
dary; persistent and sharply bordered apertures in 
such an assemblage are a priori as improbable, if not 
impossible, as straight, narrow holes running through 
a swarm of bees. 

The difficulty of these questions indicates one of 
the reasons why it has been suggested that the seem- 
ing gaps, or many of them, are not openings at all, 
but opaque screens cutting off the light from stars 
behind them. That this is quite possible in some cases 
is shown by Barnard's later photographs, particularly 
those of the singular region around the star Rho 
Ophiuchi. Here are to be seen sombre lanes and 
patches, apparently forming a connected system 
which covers an immense space, and which their dis- 
coverer thinks may constitute a ''dark nebula." This 
seems at first a startling suggestion; but, after all, 
why should there not be dark nebulas as well as 
visible ones? In truth, it has troubled some as- 

lO 



WINDOWS OF ABSOLUTE NIGHT 

tronomers to explain the luminosity of the bright 
nebulae, since it is not to be supposed that matter in 
so diffuse a state can be incandescent through heat, 
and phosphorescent light is in itself a mystery. The 
supposition is also in accord with what we know of 
the existence of dark solid bodies in space. Many 
bright stars are accompanied by obscure companions, 
sometimes as massive as themselves; the planets are 
non-luminous; the same is true of meteors before 
they plunge into the atmosphere and become heated 
by friction; and many plausible reasons have been 
found for believing that space contains as many ob- 
scure as shining bodies of great size. It is not so 
difficult, after all, then, to believe that there are im- 
mense collections of shadowy gases and meteoric dust 
whose presence is only manifested when they inter- 
cept the light coming from shining bodies behind 
them. 

This would account for the apparent extinguish- 
ment of light in open space, which is indicated by the 
falling off in relative number of telescopic stars below 
the tenth magnitude. Even as things are, the amount 
of light coming to us from stars too faint to be seen 
with the naked eye is so great that the statement of 
it generally surprises persons who are unfamiliar 
with the inner facts of astronomy. It has been cal- 
culated that on a clear night the total starlight from 
the entire celestial sphere amounts to one-sixtieth of 
the light of the full moon; but of this less than one- 
twenty-fifth is due to stars separately distinguished 
by the eye. If there were no obscuring medium in 
space, it is probable that the amount of starlight 

II 



CURIOSITIES OF THE SKY 

would be noticeably and perhaps enormously in- 
creased. 

But while it seems certain that some of the obscure 
spots in the Milky Way are due to the presence of 
"dark nebulse," or concealing veils of one kind or 
another, it is equally certain that there are many 
which are true apertures, however they may have 
been formed, and by whatever forces they may be 
maintained. These, then, are veritable windows of 
the Galaxy, and when looking out of them one is 
face to face with the great mystery of infinite space. 
There the known universe visibly ends, but mani- 
festly space itself does not end there. It is not within 
the power of thought to conceive an end to space, 
for the instant we think of a terminal point or line the 
mind leaps forward to the beyond. There must be 
space outside as well as inside. Eternity of time and 
infinity of space are ideas that the intellect cannot 
fully grasp, but neither can it grasp the idea of a 
limitation to either space or time. The metaphysical 
conceptions of hypergeometry, or fourth-dimensional 
space, do not aid us. 

Having, then, discovered that the universe is a thing 
contained in something indefinitely greater than itself ; 
having looked out of its windows and found only the 
gloom of starless night outside — what conclusions are 
we to draw concerning the beyond? It seems as 
empty as a vacuum, but is it really so ? If it be, then 
our universe is a single atom astray in the infinite; 
it is the only island in an ocean without shores; it 
is the one oasis in an illimitable desert. Then the 
Milky Way, with its wide-flung garland of stars, is 

12 



WINDOWS OF ABSOLUTE NIGHT 

afloat like a tiny smoke-wreath amid a horror of 
immeasurable vacancy, or it is an evanescent and 
solitary ring of sparkling froth cast up for a moment 
on the viewless billows of immensity. From such 
conclusions the mind instinctively shrinks. It pre- 
fers to think that there is something beyond, though 
we cannot see it. Even the universe could not bear 
to be alone — a Crusoe lost in the Cosmos! As the 
inhabitants of the most elegant chateau, with its 
gardens, parks, and crowds of attendants, would die 
of loneliness if they did not know that they have 
neighbors, though not seen, and that a living world 
of indefinite extent surrounds them, so we, when we 
perceive that the universe has limits, wish to feel that 
it is not solitary; that beyond the hedges and the 
hills there are other centres of life and activity. 
Could anything be more terrible than the thought of 
an isolated universe f The greater the being, the 
greater the aversion to seclusion. Only the infinite 
satisfies; in that alone the mind finds rest. 

We are driven, then, to believe that the universal 
night which envelops us is not tenantless; that as 
we stare out of the star-framed windows of the 
Galaxy and see nothing but uniform blackness, the 
fault is with our eyes or is due to an obscuring me- 
dium. Since our universe is limited in extent, there 
must be other universes beyond it on all sides. Per- 
haps if we could carry our telescopes to the verge of 
the great '* Coal-sack" near the "Cross," being then 
on the frontier of our starry system, we could discern, 
sparkling afar off in the vast night, some of the outer 
galaxies. They may be grander than ours, just as 

13 



CURIOSITIES OF THE SKY 

many of the suns surrounding us are immensely 
greater than ours. If we could take our stand some- 
where in the midst of immensity and, with vision of 
infinite reach, look about us, we should perhaps see a 
countless number of stellar systems, amid which ours 
would be unnoticeable, like a single star among the 
multitude glittering in the terrestrial sky on a clear 
night. Some might be in the form of a wreath, like 
our own ; some might be globular, like the great star- 
clusters in Hercules and Centaurus; some might be 
glittering circles, or disks, or rings within rings. If 
we could enter them we should probably find a vast 
variety of composition, including elements unknown 
to terrestrial chemistry ; for while the visible universe 
appears to contain few if any substances not existing 
on the earth or in the sun, we have no warrant to 
assume that others may not exist in infinite space. 

And how as to gravitation ? We do not know that 
gravitation acts beyond the visible universe, but it 
is reasonable to suppose that it does. At any rate, 
if we let go its sustaining hand we are lost, and can only 
wander hopelessly in our speculations, like children 
astray. If the empire of gravitation is infinite, then 
the various outer systems must have some, though 
measured by our standards an imperceptible, attrac- 
tive influence upon each other, for gravitation never 
lets go its hold, however great the space over which it 
is required to act. Just as the stars about us are all 
in motion, so the starry systems beyond our sight 
may be in motion, and our system as a whole may 
be moving in concert with them. If this be so, then 
after interminable ages the aspect of the entire system 

14 



WINDOWvS OF ABSOLUTE NIGHT 

of systems must change, its various members assuming 
new positions with respect to one another. In the 
course of time we may even suppose that our universe 
will approach relatively close to one of the others; 
and then, if men are yet living on the earth, they may 
glimpse through the openings which reveal nothing 
to us now, the lights of another nearing star system, 
like the signals of a strange squadron, bringing them 
the assurance (which can be but an inference at 
present) that the ocean of space has other argosies 
venturing on its limitless expanse. 

There remains the question of the luminiferous 
ether by whose agency the waves of light are borne 
through space. The ether is as mysterious as gravita- 
tion. With regard to either we only infer its exist- 
ence from the effects which we ascribe to it. Evident- 
ly the ether must extend as far as the most distant 
visible stars. But does it continue on indefinitely in 
outer space? If it does, then the invisibility of the 
other systems must be due to their distance diminish- 
ing the quantity of light that comes from them below 
the limit of perceptibility, or to the interposition of 
absorbing media; if it does not, then the reason why 
we cannot see them is owing to the absence of a 
means of conveyance for the light-waves, as the lack 
of an interplanetary atmosphere prevents us from 
hearing the thunder of sun-spots. (It is interesting 
to recall that Mr. Edison was once credited with the 
intention to construct a gigantic microphone which 
should render the roar of sun-spots audible by trans- 
forming the electric vibrations into sound-waves.) 
On this supposition each starry system would be en- 

15 



CURIOSITIES OF THE SKY 

veloped in its own globule of ether, and no light could 
cross from one to another. But the probability is 
that both the ether and gravitation are ubiquitous, 
and that all the stellar systems are immersed in the 
former like clouds of phosphorescent organisms in 
the sea. 

So astronomy carries the mind from height to 
greater height. Men were long in accepting the 
proofs of the relative insignificance of the earth; 
they were more quickly convinced of the comparative 
littleness of the solar system; and now the evidence 
assails their reason that what they had regarded as 
the universe is only one mote gleaming in the sun- 
beams of Infinity. 



II 

STAR-CLOUDS, STAR-CLUSTERS, AND STAR-STREAMS 

IN the preceding chapter we have seen something 
of the strangely compHcated structure of the 
Galaxy, or Milky Way. We now proceed to study 
more comprehensively that garlanded "Pathway of 
the Gods." 

Judged by the eye alone, the Milky Way is one of 
the most delicately beautiful phenomena in the entire 
realm of nature — a shimmer of silvery gauze stretched 
across the sky; but studied in the light of its revela- 
tions, it is the most stupendous object presented to 
human ken. Let us consider, first, its appearance to 
ordinary vision. Its apparent position in the sky 
shifts according to the season. On a serene, cloudless 
summer evening, in the absence of the moon, whose 
light obscures it, one sees the Galaxy spanning the 
heavens from north to southeast of the zenith like a 
phosphorescent arch. In early spring it forms a 
similar but, upon the whole, less brilliant arch west of 
the zenith. Between spring and summer it lies like 
a long, faint twilight band along the northern horizon. 
At the beginning of winter it again forms an arch, 
this time spanning the sky from east to west, a little 
north of the zenith. These are its positions as 

17 



CURIOSITIES OF THE SKY 

viewed from the mean latitude of tlie United States. 
Even the beginner in star-gazing does not have to 
watch it throughout the year in order to be convinced 
that it is, in reaHty, a great circle, extending entirely 
around the celestial sphere. We appear to be situ- 
ated near its centre, but its periphery is evidently far 
away in the depths of space. 

Although to the casual observer it seems but a 
delicate scarf of light, brighter in some places than in 
others, but hazy and indefinite at the best, such is 
not its appearance to those who study it with care. 
They perceive that it is an organic whole, though 
marvellously complex in detail. The telescope shows 
that it consists of stars too faint and small through 
excess of distance to be separately visible. Of the 
hundred million suns which some estimates have fixed 
as the probable population of the starry universe, 
the vast majority (at least thirty to one) are included 
in this strange belt of misty light. But they are not 
uniformly distributed in it; on the contrary, they 
are arrayed in clusters, knots, bunches, clouds, and 
streams. The appearance is somewhat as if the 
Galaxy consisted of innumerable swarms of silver- 
winged bees, more or less intermixed, some massed 
together, some crossing the paths of others, but all 
governed by a single purpose which leads them to 
encircle the region of space in which we are situ- 
ated. 

From the beginning of the systematic study of the 
heavens, the fact has been recognized that the form 
of the Milky Way denotes the scheme of the sidereal 
system. At first it was thought that the shape of the 

i8 



STAR CLOUDS, CLUSTERS, AND STREAMS 

system was that of a vast round disk, flat like a cheese, 
and filled with stars, our sun and his relatively few 
neighbors being placed near the centre. According 
to this view, the galactic belt was an effect of per- 
spective ; for when looking in the direction of the plane 
of the disk, the eye ranged through an immense ex- 
tension of stars which blended into a glimmering blur, 
surrounding us like a ring; while when looking out 
from the sides of the disk we saw but few stars, and in 
those directions the heavens appeared relatively 
blank. Finally it was recognized that this theory 
did not correspond with the observed appearances, 
and it became evident that the Milky Way was not 
a mere effect of perspective, but an actual band of 
enormously distant stars, forming a circle about the 
sphere, the central opening of the ring (containing 
many scattered stars) being many times broader than 
the width of the ring itself. Our sun is one of the 
scattered stars in the central opening. 

As already remarked, the ring of the Galaxy is very 
irregular, and in places it is partly broken. With 
its sinuous outline, its pendant sprays, its graceful 
and accordant curves, its bunching of masses, its 
occasional interstices, and the manifest order of a 
general plan governing the jumble of its details, it 
bears a remarkable resemblance to a garland — a fact 
which appears the more wonderful when we recall its 
composition. That an elm -tree should trace the 
lines of beauty with its leafy and pendulous branches 
does not surprise us; but we can only gaze with 
growing amazement when we behold a hundred 
million suns imitating the form of a chaplet! And 

19 



CURIOSITIES OF THE SKY 

then we have to remember that this form furnishes 
the ground-plan of the universe. 

As an indication of the extraordinary speculations 
to which the mystery of the Milky Way has given rise, 
a theory recently (1909) proposed by Prof. George C. 
Comstock may be mentioned. Starting with the 
data (first) that the number of stars increases as 
the Milky Way is approached, and reaches a maxi- 
mum in its plane, while on the other hand the number 
of nebulae is greatest outside the Milky Way and in- 
creases with distance from it, and (second) that the 
Milky Way, although a complete ring, is broad and 
diffuse on one side through one-half its course — ^that 
half alone containing nebulae — and relatively narrow 
and well defined on the opposite side, the author 
of this singular speculation avers that these facts can 
best be explained by supposing that the invisible 
universe consists of two interpenetrating parts, one 
of which is a chaos of indefinite extent, strewn with 
stars and nebulous dust, and the other a long, broad 
but comparatively thin cluster of stars, including the 
sun as one of its central members. This fiat star- 
cluster is conceived to be moving edgewise through 
the chaos, and, according to Professor Comstock, it 
acts after the manner of a snow-plough sweeping away 
the cosmic dust and piling it on either hand above and 
below the plane of the moving cluster. It thus forms 
a transparent rift, through which we see farther and 
command a view of more stars than through the in- 
tensified dust-clouds on either hand. This rift is the 
Milky Way. The dust thrown aside toward the poles 
of the Milky Way is the substance of the nebulae 

20 



STAR CLOUDS, CLUSTERS, AND STREAMS 

which abound there. Ahead, where the front of the 
star-plough is clearing the way, the chaos is nearer 
at hand, and consequently there the rift subtends a 
broader angle, and is filled with primordial dust, 
which, having been annexed by the vanguard of the 
star-swarm, forms the nebulae seen only in that part 
of the Milky Way. But behind, the rift appears 
narrow because there we look farther away between 
dust-clouds produced ages ago by the front of the 
plough, and no scattered dust remains in that part of 
the rift. 

In quoting an outline of this strikingly original 
theory the present writer should not be understood 
as assenting to it. That it appears bizarre is not, in 
itself, a reason for rejecting it, when we are dealing 
with so problematical and enigmatical a subject as the 
Milky Way; but the serious objection is that the 
theory does not sufficiently accord with the observed 
phenomena. There is too much evidence that the 
Milky Way is an organic system, however fantastic 
its form, to permit the belief that it can only be a 
rift in chaotic clouds. As with every organism, we 
find that its parts are more or less clearly repeated 
in its ensemble. Among all the strange things that 
the Milky Way contains there is nothing so extraor- 
dinary as itself. Every astronomer must many 
times have found himself marvelling at it in those 
comparatively rare nights when it shows all its 
beauty and all its strangeness. In its great broken 
rifts, divisions, and spirals are found the gigantic 
prototypes of similar forms in its star-clouds and 
clusters. As we have said, it determines the general 

21 



CURIOSITIES OF THE SKY 

shape of the whole sidereal system. Some of the 
brightest stars in the sky appear to hang like jewels 
suspended at the ends of tassels dropped from the 
Galaxy. Among these pendants are the Pleiades 
and the Hyades. Orion, too, the "Mighty Hunter,'' 
is caught in "a loop of light" thrown out from it. 
The majority of the great first-magnitude stars seem 
related to it, as if they formed an inner ring inclined 
at an angle of some twenty degrees to its plane. 
Many of the long curves that set off from it on both 
sides are accompanied by corresponding curves of 
lucid stars. In a word, it offers every appearance 
of structural connection with the entire starry system. 
That the universe should have assumed the form of 
a wreath is certainly a matter for astonishment ; but 
it would have been still more astonishing if it had 
been a cube, a rhomboid, or a dodecahedron, for 
then we should have had to suppose that something 
resembling the forces that shape crystals had acted 
upon the stars, and the difficulty of explaining the 
universe by the law of gravitation would have been 
increased. 

From the Milky Way as a whole we pass to the vast 
clouds, swarms, and clusters of stars of which it is 
made up. It may be, as some astronomers hold, 
that most of the galactic stars are much smaller than 
the sun, so that their faintness is not due entirely to 
the effect of distance. Still, their intrinsic brilliance 
attests their solar character, and considering their 
remoteness, which has been estimated at not less than 
ten thousand to twenty thousand light-years (a light- 
year is equal to nearly six thousand million miles) 

22 



STAR CLOUDS, CLUSTERS, AND STREAMS 

their actual masses cannot be extremely small. The 
minutest of them are entitled to be regarded as real 
suns, and they vary enormously in magnitude. The 
effects of their attractions upon one another can only 
be inferred from their clustering, because their 
relative movements are not apparent on account of 
the brevity of the observations that we can make. 
But imagine a being for whom a million years would 
be but as a flitting moment; to him the Milky Way 
would appear in a state of ceaseless agitation — swirl- 
ing with *'a fury of whirlpool motion." 

The cloud-like aspect of large parts of the Galaxy 
must always have attracted attention, even from 
naked-eye observers, but the true star-clouds were 
first satisfactorily represented in Barnard's photo- 
graphs. The resemblance to actual clouds is often 
startling. Some are close-packed and dense, like 
cumuli; some are wispy or mottled, like cirri. The 
rifts and modulations, as well as the general outlines, 
are the same as those of clouds of vapor or dust, and 
one notices also the characteristic thinning out at the 
edges. But we must beware of supposing that the 
component suns are thickly crowded as the particles 
forming an ordinary cloud. They look, indeed, as if 
they were matted together, because of the irradiation 
of light, but in reality millions and billions of miles 
separate each star from its neighbors. Nevertheless 
they form real assemblages, whose members are far 
more closely related to one another than is our sun 
to the stars around him, and if we were in the Milky 
Way the aspect of the nocturnal sky would be mar- 
vellously different from its present appearance. 

23 



CURIOSITIES OF THE SKY 

Stellar clouds are characteristic of the Galaxy and 
are not found beyond its borders, except in the 
"Magellanic Clouds" of the southern hemisphere, 
which resemble detached portions of the Milky Way. 
These singular objects form as striking a peculiarity of 
the austral heavens as does the great "Coal -sack" 
described in Chapter I. But it is their isolation that 
makes them so remarkable, for their composition is 
essentially galactic, and if they were included within 
its boundaries they would not appear more wonderful 
than many other parts of the Milky Way. Placed 
where they are, they look like masses fallen from the 
great stellar arch. They are full of nebulae and star- 
clusters, and show striking evidences of spiral move- 
ment. 

Star-swarms, which are also characteristic features 
of the Galaxy, differ from star-clouds very much in 
the way that their name would imply — i.e., their 
component stars are so arranged, even when they are 
countless in number, that the idea of an exceedingly 
numerous assemblage rather than that of a cloud is 
impressed on the observer's mind. In a star-swarm 
the separate members are distinguishable because 
they are either larger or nearer than the stars com- 
posing a "cloud." A splendid example of a true 
star-swarm is furnished by Chi Persei, in that part of 
the Milky Way which runs between the constella- 
tions Perseus and Cassiopeia. This swarm is much 
coarser than many others, and can be seen by the 
naked eye. In a small telescope it appears double, 
as if the suns composing it had divided into two 
parties which keep on their way side by side, with 

24 



STAR CLOUDS, CLUSTERS, AND STREAMS 

some commingling of their members where the skirts 
of the two companies come in contact. 

Smaller than either star-clouds or star-swarms, and 
differing from both in their organization, are star- 
clusters. These, unlike the others, are found outside 
as well as inside the Milky Way, although they are 
more numerous inside its boundaries than elsewhere. 
The term star-cluster is sometimes applied, though 
improperly, to assemblages which are rather groups, 
such, for instance, as the Pleiades. In their most 
characteristic aspect star-clusters are of a globular 
shape — globes of suns! A famous example of a 
globular star-cluster, but one not included in the 
Milky Way, is the ''Great Cluster in Hercules." 
This is barely visible to the naked eye, but a small 
telescope shows its character, and in a large one it 
presents a marvellous spectacle. Photographs of 
such clusters are, perhaps, less effective than those of 
star-clouds, because the central condensation of stars 
in them is so great that their light becomes blended 
in an indistinguishable blur. The beautiful effect of 
the incessant play of infinitesimal rays over the 
apparently compact surface of the cluster, as if it 
were a globe of the finest frosted silver shining in an 
electric beam, is also lost in a photograph. Still, 
even to the eye looking directly at the cluster through 
a powerful telescope, the central part of the wonderful 
congregation seems almost a solid mass in which the 
stars are packed like the ice crystals in a snowball. 

The same question rises to the lips of every ob- 
server: How can they possibly have been brought 
into such a situation? The marvel does not grow 

25 



CURIOSITIES OF THE SKY 

less when we know that, instead of being closely com- 
pacted, the stars of the cluster are probably separated 
by millions of miles ; for we know that their distances 
apart are slight as compared with their remoteness 
from the earth. Sir William Herschel estimated 
their number to be about fourteen thousand, but in 
fact they are uncountable. If we could view them 
from a point just within the edge of the assemblage, 
they would offer the appearance of a hollow hemi- 
sphere emblazoned with stars of astonishing brill- 
iancy; the near-by ones unparalleled in splendor by 
any celestial object known to us, while the more dis- 
tant ones would resemble ordinary stars. An in- 
habitant of the cluster would not know, except by a 
process of ratiocination, that he was dwelling in a 
globular assemblage of suns; only from a point far 
outside would their spherical arrangement become 
evident to the eye. Imagine fourteen thousand fire- 
balloons arranged with an approach to regularity in 
a spherical space — say, ten miles in diameter; there 
would be an average of less than thirty in every 
cubic mile, and it would be necessary to go to a con- 
siderable distance in order to see them as a globular 
aggregation; yet from a point sufficiently far away 
they would blend into a glowing ball. 

Photographs show even better than the best tele- 
scopic views that the great clust^^ is surrounded with 
a multitude of dispersed stars, suggestively arrayed 
in more or less curving lines, which radiate from the 
principal mass, with which their connection is mani- 
fest. These stars, situated outside the central sphere, 
look somewhat like vagrant bees buzzing round a dense 

26 




STAR-CLUSTER IN HERCULES 
(Photographed with a two-foot reflector) 



STAR CLOUDS, CLUSTERS, AND STREAMS 

swarm where the queen bee is settling. Yet while 
there is so much to suggest the operation of central 
forces, bringing and keeping the members of the 
cluster together, the attentive observer is also im- 
pressed with the idea that the whole wonderful 
phenomenon may be the result of explosion. As soon 
as this thought seizes the mind, confirmation of it 
seems to be found in the appearance of the outlying 
stars, which could be as readily explained by the 
supposition that they have been blown apart as that 
they have flocked together toward a centre. The 
probable fact that the stars constituting the cluster 
are very much smaller than our sun might be regarded 
as favoring the hypothesis of an explosion. Of their 
real size we know nothing, but, on the basis of an 
uncertain estimate of their parallax, it has been cal- 
culated that they may average forty-five thousand 
miles in diameter — something more than half the 
diameter of the planet Jupiter. Assuming the same 
mean density, fourteen thousand such stars might 
have been formed by the explosion of a body about 
twice the size of the sun. This recalls the theory 
of Olbers, which has never been altogether abandoned 
or disproved, that the Asteroids were formed by the 
explosion of a planet circulating between the orbits 
of Mars and Jupiter. The Asteroids, whatever their 
manner of origin, form a ring around the sun; but, 
of course, the explosion of a great independent body, 
not originally revolving about a superior centre of 
gravitative force, would not result in the formation 
of a ring of small bodies, but rather of a dispersed 
mass of them. But back of any speculation of this 

29 



CURIOSITIES OF THE SKY 

kind lies the problem, at present insoluble: How 
could the explosion be produced ? (See the question 
of explosions in Chapters VI and XIV.) 

Then, on the other hand, we have the observation 
of Herschel, since abundantly confirmed, that space 
is unusually vacant in the immediate neighborhood of 
condensed star-clusters and nebulae, which, as far as 
it goes, might be taken as an indication that the 
assembled stars had been drawn together by their 
mutual attractions, and that the tendency to aggre- 
gation is still bringing new members toward the 
cluster. But in that case there must have been 
an original condensation of stars at that point in 
space. This could probably have been produced by 
the coagulation of a great nebula into stellar nuclei, 
a process which seems now to be taking place in the 
Orion Nebula. 

A yet more remarkable globular star-cluster exists 
in the southern hemisphere. Omega Centauri. In 
this case the central condensation of stars presents 
an almost uniform blaze of light. Like the Hercules 
cluster, that in Centaurus is surrounded with stars 
scattered over a broad field and showing an appear- 
ance of radial arrangement. In fact, except for its 
greater richness, Omega Centauri is an exact duplicate 
of its northern rival. Each appears to an imaginative 
spectator as a veritable *'city of suns." Mathe- 
matics shrinks from the task of disentangling the 
maze of motions in such an assemblage. • It would seem 
that the chance of collisions is not to be neglected, 
and this idea finds a certain degree of confirmation 
in the appearance of ** temporary stars'* which have 

30 




GREAT SOUTHERN STAR-CLUSTER, OMEGA CENTAURI 



STAR CLOUDS, CLUSTERS, AND STREAMS 

more than once blazed out in, or close by, globular 
star-clusters. 

This leads up to the notable fact, first established 
by Professor Bailey a few years ago, that such clusters 
are populous with variable stars. Omega Centauri 
and the Hercules cluster are especially remarkable in 
this respect. The variables found in them are all 
of short period and the changes of light show a note- 
worthy tendency to uniformity. The first thought 
is that these phenomena must be due to collisions 
among the crowded stars, but, if so, the encounters 
cannot be between the stars themselves, but probably 
between stars and meteor swarms revolving around 
them. Such periodic collisions might go on for ages 
without the meteors being exhausted by incorpora- 
tion with the stars. This explanation appears all 
the more probable because one would naturally ex- 
pect that flocks of meteors would abound in a close 
aggregation of stars. It is also consistent with 
Perrine's discovery — that the globular star-clusters 
are powdered with minute stars strewn thickly among 
the brighter ones. 

In speaking of Professor Comstock's extraordinary 
theory of the Milky Way, the fact was mentioned that, 
broadly speaking, the nebulae are less numerous in 
the galactic belt than in the comparatively open 
spaces on either side of it, but that they are, neverthe- 
less, abundant in the broader half of the Milky Way 
which he designates as the front of the gigantic 
** plough" supposed to be forcing its way through 
the enveloping chaos. In and around the Sagit- 
tarius region the intermingling of nebulas and 

33 



CURIOSITIES OF THE SKY 

galactic star clouds and clusters is particularly re- 
markable. That there is a causal connection no 
thoughtful observer can doubt. We are unable to 
get away from the evidence that a nebula is like a 
seed-ground from which stars spring forth; or we 
may say that nebulas resemble clouds in whose 
bosom raindrops are forming. The wonderful as- 
pect of the admixtures of nebula and star-clusters 
in Sagittarius has been described in Chapter I. We 
now come to a stiU more extraordinary phenomenon 
of this kind — ^the Pleiades nebulas. 

The group of the Pleiades, although lying outside 
the main course of the Galaxy, is connected with it 
by a faint loop, and is the scene of the most remark- 
able association of stars and nebulous matter known 
in the visible universe. The naked eye is unaware 
of the existence of nebulas in the Pleiades, or, at the 
best, merely suspects that there is something of the 
kind there; and even the most powerful telescopes 
are far from revealing the full wonder of the spectacle ; 
but in photographs which have been exposed for 
many hours consecutively, in order to accumulate the 
impression of the actinic rays, the revelation is stun- 
ning. The principal stars are seen surrounded by, 
and, as it were, drowned in, dense nebulous clouds of 
an unparalleled kind. The forms assumed by these 
clouds seem at first sight inexplicable. They look 
like fleeces, or perhaps more like splashes and daubs 
of luminous paint dashed carelessly from a brush. 
But closer inspection shows that they are, to a large 
extent, woven out of innumerable threads of filmy 
texture, and there are many indications of spiral 

34 




«3 

w 

Q 
< 

W 



STAR CLOUDS, CLUSTERS, AND STREAMS 

tendencies. Each of the bright stars of the group — 
Alcyone, Merope, Maia, Electra, Taygeta, Atlas — is 
the focus of a dense fog (totally invisible, remember, 
alike to the naked eye and to the telescope), and these 
particular stars are veiled from sight behind the 
strange mists. Running in all directions across the 
relatively open spaces are nebulous wisps and streaks 
of the most curious forms. On some of the nebular 
lines, which are either straight throughout, or if they 
change direction do so at an angle, little stars are 
strung like beads. In one case seven or eight stars 
are thus aligned, and, as if to emphasize their depend- 
ence upon the chain which connects them, when it 
makes a slight bend the file of stars turns the same 
way. Many other star rows in the group suggest by 
their arrangement that they, too, were once strung 
upon similar threads which have now disappeared, 
leaving the stars spaced along their ancient tracks. 
We seem forced to the conclusion that there was a 
time when the Pleiades were embedded in a vast 
nebula resembling that of Orion, and that the cloud 
has now become so rare by gradual condensation 
into stars that the merest trace of it remains, and this 
would probably have escaped detection but for the 
remarkable actinic power of the radiant matter of 
which it consists. The richness of many of these 
faint nebulous masses in ultra-violet radiations, 
which are those that specially affect the photographic 
plate, is the cause of the marvellous revelatory power 
of celestial photography. So the veritable unseen 
universe, as distinguished from the ''unseen universe" 
of metaphysical speculation, is shown to us. 

37 



--CURIOSITIES OF THE SKY 

A different kind of association between stars and 

nebulae is shown in some surprising photographic 
objects in' the constellation Cygnus, where long, wispy- 
nebula, billions of miles in length, some of them 
looking like tresses streaming in a breeze, lie amid 
fields of stars which seem related to them. But the 
relation is of a most singular kind, for notwithstand- 
ing the delicate structure of the long nebula they ap- 
pear to act as barriers, causing the stars to heap 
themselves on one side. The stars are two, three, or 
four times as numerous on one side of the nebulas as 
on the other. These nebulae, as far as appearance 
goes, might be likened to rail fences, or thin hedges, 
against which the wind is driving drifts of powdery 
snow, which, while scattered plentifully all around, 
tends to bank itself on the leeward side of the ob- 
struction. The imagination is at a loss to account 
for these extraordinary phenomena; yet there they 
are, faithfully giving us their images whenever the 
photographic plate is exposed to their radiations. 

Thus the more we see of the universe with improved 
methods of observation, and the more we invent aids 
to human senses, each enabling us to penetrate a 
little deeper into the unseen, the greater becomes the 
mystery. The telescope carried us far, photography 
is carrying us still farther ; but what as yet unimagined 
instrument will take us to the bottom, the top, and 
the end ? And then, what hitherto untried power of 
thought will enable us to comprehend the meaning of 
it all? 



Ill 

STELLAR MIGRATIONS 

TO the untrained eye the stars and the planets are 
not distinguishable. It is customary to call 
them all alike ''stars." But since the planets more 
or less rapidly change their places in the sky, in 
consequence of their revolution about the sun, while 
the stars proper seem to remain always in the same 
relative positions, the latter are spoken of as "fixed 
stars." In the beginnings of astronomy it was not 
known that the ''fixed stars" had any motion in- 
dependent of their apparent annual revolution with 
the whole sky about the earth as a seeming centre. 
Now, however, we know that the term "fixed stars" 
is paradoxical, for there is not a single really fixed 
object in the whole celestial sphere. The apparent 
fixity in the positions of the stars is due to their im- 
mense distance, combined with the shortness of the 
time during which we are able to observe them. It 
is like viewing the plume of smoke issuing from a 
steamer, hull down, at sea : if one does not continue to 
watch it for a long time it appears to be motionless, 
although in reality it may be travelling at great speed 
across the line of sight. Even the planets seem fixed 
in position if one watches them for a single night only, 
3 39 



CURIOSITIES OF THE SKY 

and the more distant ones do not sensibly change their 
places, except after many nights of observation. 
Neptune, for instance, moves but little more than 
two degrees in the course of an entire year, and in a 
month its change of place is only about one-third of 
the diameter of the full moon. 

Yet, fixed as they seem, the stars are actually 
moving with a speed in comparison with which, in 
some cases, the planets might almost be said to stand 
fast in their tracks. Jupiter's speed in his orbit is 
about eight miles per second, Neptune's is less than 
three and one-half miles, and the earth's is about 
eighteen and one-half miles; while there are ''fixed 
stars'" which move two hundred or three hundred 
miles per second. They do not all, however, move 
with so great a velocity, for some appear to travel 
no faster than the planets. But in all cases, notwith- 
standing their real speed, long-continued and exceed- 
ingly careful observations are required to demonstrate 
that they are moving at all. No more overwhelming 
impression of the frightful depths of space in which 
the stars are buried can be obtained than by reflect- 
ing upon the fact that a star whose actual motion 
across the line of sight amounts to two hundred miles 
per second does not change its apparent place in the 
sky, in the course of a thousand years, sufficiently to 
be noticed by the casual observer of the heavens! 

There is one vast difference between the motions 
of the stars and those of the planets to which atten- 
tion should at once be called: the planets, being under 
the control of a central force emanating from their 
immediate master, the sun, all move in the same 

40 



STELLAR MIGRATIONS 

direction and in orbits concentric about the sun; 
the stars, on the other hand, move in every conceivable 
direction and have no apparent centre of motion, for 
all efforts to discover such a centre have failed. At 
one time, when theology had finally to accept the 
facts of science, a grandiose conception arose in some 
pious minds, according to which the Throne of God 
was situated at the exact centre of His Creation, and, 
seated there. He watched the magnificent spectacle 
of the starry systems obediently revolving around 
Him. Astronomical discoveries and speculations 
seemed for a time to afford some warrant for this 
view, which was, moreover, an acceptable substitute 
for the abandoned geocentric theory in minds that 
could only conceive of God as a superhuman artificer, 
constantly admiring His own work. No longer ago 
than the middle of the nineteenth century a German 
astronomer, Maedler, believed that he had actually 
found the location of the centre about which the 
stellar universe revolved. He placed it in the group 
of the Pleiades, and upon his authority an extraor- 
dinary imaginative picture was sometimes drawn of 
the star Alcyone, the brightest of the Pleiades, as 
the very seat of the Almighty. This idea even seemed 
to gain a kind of traditional support from the mystic 
significance, without known historical origin, which 
has for many ages, and among widely separated 
peoples, been attached to the remarkable group of 
which Alcyone is the chief. But since Maedler's 
time it has been demonstrated that the Pleiades 
cannot be the centre of revolution of the universe, 
and, as already remarked, all attempts to find or fix 

41 



CURIOSITIES OF THE SKY 

such a centre have proved abortive. Yet so powerful 
was the hold that the theory took upon the popular 
imagination, that even to-day astronomers are often 
asked if Alcyone is not the probable site of "Jerusalem 
the Golden." 

If there were a discoverable centre of predominant 
gravitative power, to which the motions of all the 
stars could be referred, those motions would ap- 
pear less mysterious, and we should then be able 
to conclude that the universe was, as a whole, a proto- 
type of the subsidiary systems of which it is com- 
posed. We should look simply to the law of gravita- 
tion for an explanation, and, naturally, the centre 
would be placed within the opening enclosed by the 
Milky Way. If it were there the Milky Way itself 
should exhibit signs of revolution about it, like a 
wheel turning upon its hub. No theory of the star 
motions as a whole could stand which failed to take 
account of the Milky Way as the basis of all. But 
the very form of that divided wreath of stars forbids 
the assumption of its revolution around a centre. 
Even if it could be conceived as a wheel having no 
material centre it would not have the form which it 
actually presents. As was shown in Chapter II, there 
is abundant evidence of motion in the Milky Way; 
but it is not motion of the system as a whole, but 
motion affecting its separate parts. Instead of all 
moving one way, the galactic stars, as far as their 
movements can be inferred, are governed by local 
influences and conditions. They appear to travel 
crosswise and in contrary directions, and perhaps 
they eddy around foci where great numbers have 

42 



STELLAR MIGRATIONS 

assembled; but of a universal revolution involving 
the entire mass we have no evidence. 

Most of our knowledge of star motions, called ** prop- 
er motions," relates to individual stars and to a few 
groups which happen to be so near that the effects 
of their movements are measurable. In some cases 
the motion is so rapid (not in appearance, but in 
reality) that the chief difficulty is to imagine how it 
can have been imparted, and what will eventually 
become of the ** runaways." Without a collision, 
or a series of very close approaches to great gravita- 
tive centres, a star travelling through space at the 
rate of two hundred or three hundred miles per second 
could not be arrested or turned into an orbit which 
would keep it forever flying within the limits of the 
visible universe. A famous example of these speed- 
ing stars is "1830 Groombridge," a star of only the 
sixth magnitude, and consequently just visible to the 
naked eye, whose motion across the line of sight is so 
rapid that it moves upon the face of the sky a distance 
equal to the apparent diameter of the moon every 
280 years. The distance of this star is at least 
200,000,000,000,000 miles, and may be two or three 
times greater, so that its actual speed cannot be less 
than two hundred, and may be as much as four hun- 
dred, miles per second. It could be turned into a new 
course by a close approach to a great sun, but it 
could only be stopped by collision, head-on, with a 
body of enormous mass. Barring such accidents it 
must, as far as we can see, keep on until it has traversed 
our stellar system, whence it may escape and pass out 
into space beyond, to join, perhaps, one of those 

43 



CURIOSITIES OF THE SKY 

other universes of which we have spoken. Arcturus, 
one of the greatest suns in the universe, is also a run- 
away, whose speed of flight has been estimated all the 
way from fifty to two hundred miles per second. 
Arcturus, we have every reason to believe, possesses 
hundreds of times the mass of our sun — think, then, 
of the prodigious momentum that its motion implies ! 
Sirius moves more moderately, its motion across the 
line of sight amounting to only ten miles per second, 
but it is at the same time approaching the sun at 
about the same speed, its actual velocity in space 
being the resultant of the two displacements. 

What has just been said about the motion of Sirius 
brings us to another aspect of this subject. The 
fact is, that in every case of stellar motion the dis- 
placement that we observe represents only a part of 
the actual movement of the star concerned. There 
are stars whose motion carries them straight toward 
or straight away from the earth, and such stars, of 
course, show no cross motion. But the vast majority 
are travelling in paths inclined from a perpendicular 
to our line of sight. Taken as a whole, the stars may 
be said to be flying about like the molecules in a mass 
of gas. The discovery of the radial component in the 
movements of the stars is due to the spectroscope. 
If a star is approaching, its spectral lines are shifted 
toward the violet end of the spectrum by an amount 
depending upon the velocity of approach; if it is 
receding, the lines are correspondingly shifted toward 
the red end. Spectroscopic observation, then, com- 
bined with micrometric measurement of the cross 
motion, enables us to detect the real movement of 

44 



STELLAR MIGRATIONS 

the star in space. Sometimes it happens that a 
star's radial movement is periodically reversed; first 
it approaches, and then it recedes. This indicates 
that it is revolving around a near-by companion, which 
is often invisible, and superposed upon this motion is 
that of the two stars concerned, which together may 
be approaching or receding or travelling across the 
line of sight. Thus the complications involved in the 
stellar motions are often exceedingly great and 
puzzling. 

Yet another source of complication exists in the 
movement of our own star, the sun. There is no 
more difficult problem in astronomy than that of 
disentangling the effects of the solar motion from 
those of the motions of the other stars. But the 
problem, difficult as it is, has been solved, and upon its 
solution depends our knowledge of the speed and 
direction of the movement of the solar system 
through space, for of course the sun carries its planets 
with it. One element of the solution is found in the 
fact that, as a result of perspective, the stars toward 
which we are going appear to move apart toward all 
points of the compass, while those behind appear to 
close up together. Then the spectroscopic principle 
already mentioned is invoked for studying the shift 
of the lines, which is toward the violet in the stars 
ahead of us and toward the red in those that we are 
leaving behind. Of course the effects of the independ- 
ent motions of the stars must be carefully excluded. 
The result of the studies devoted to this subject is to 
show that we are travelling at a speed of twelve to 
fifteen miles per second in a northerly direction, 

45 



CURIOSITIES OF THE SKY 

toward the border of the constellations Hercules and 
Lyra. A curious fact is that the more recent esti- 
mates show that the direction is not very much out 
of a straight line drawn from the sun to the star 
Vega, one of the most magnificent suns in the heavens. 
But it should not be inferred from this that Vega 
is drawing us on; it is too distant for its gravitation to 
have such an effect. 

Many unaccustomed thoughts are suggested by 
this mighty voyage of the solar system. Whence 
have we come, and whither do we go ? Every year 
of our lives we advance at least 375,000,000 miles. 
Since the traditional time of Adam the sun has led 
his planets through the wastes of space no less than 
225,000,000,000 miles, or more than 2400 times the 
distance that separates him from the earth. Go 
back in imagination to the geologic ages, and try to 
comprehend the distance over which the earth has 
flown. Where was our little planet when it emerged 
out of the clouds of chaos ? Where was the sun when 
his "thunder march" began? What strange con- 
stellations shone down upon our globe when its 
masters of life were the monstrous beasts of the 
"Age of Reptiles?" A million years is not much of 
a span of time in geologic reckoning, yet a million 
years ago the earth was farther from its present place 
in space than any of the stars with a measurable 
parallax are now. It was more than seven times as 
far as Sirius, nearly fourteen times as far as Alpha 
Centauri, three times as far as Vega, and twice as far 
as Arcturus. But some geologists demand two 
hundred, three hundred, even one thousand million 

46 



STELLAR MIGRATIONS 

years to enable them to account for the evolutionary 
development of the earth and its inhabitants. In a 
thousand million years the earth would have travelled 
farther than from the remotest conceivable depths 
of the Milky Way! 

Other curious reflections arise when we think of 
the form of the earth's track as it follows the lead 
of the sun, in a journey which has neither known be- 
ginning nor conceivable end. There are probably 
many minds which have found a kind of consolation 
in the thought that every year the globe returns to the 
same place, on the same side of the sun. This idea 
may have an occult connection with our traditional 
regard for anniversaries. When that period of the 
year returns at which any great event in our lives 
has occurred we have the feeling that the earth, in its 
annual round, has, in a manner, brought us back to 
the scene of that event. We think of the earth's 
orbit as a well-worn path which we traverse many 
times in the course of a lifetime. It seems familiar 
to us, and we grow to have a sort of attachment to it. 
The sun we are accustomed to regard as a fixed centre 
in space, like the mill or pump around which the 
harnessed patient mule makes his endless circuits. 
But the real fact is that the earth never returns to the 
place in space which it has once* quitted. In con- 
sequence of the motion of the sun carrying the earth 
and the other planets along, the track pursued by our 
globe is a vast spiral in space continually developing 
and never returning upon its course. It is probable 
that the tracks of the sun and the other stars are also 
irregular, and possibly spiral, although, as far as can 

47 



CURIOSITIES OF THE SKY 

be at present determined, they appear to be prac- 
tically straight. Every star, wherever it may be 
situated, is attracted by its fellow-stars from many 
sides at once, and although the force is minimized by 
distance, yet in the course of many ages its effects 
must become manifest. 

Looked at from another side, is there not something 
immensely stimulating and pleasing to the imagina- 
tion in the idea of so stupendous a journey, which 
makes all of us the greatest of travellers? In the 
course of a long life a man is transported through 
space thirty thousand million miles; Halley's Comet 
does not travel one-quarter as far in making one of its 
immense circuits. And there are adventures on this 
voyage of which we are just beginning to learn to 
take account. Space is full of strange things, and the 
earth must encounter some of them as it advances 
through the unknown. Many singular speculations 
have been indulged in by astronomers concerning the 
possible effects upon the earth of the varying state of 
the space that it traverses. Even the alternation of 
hot and glacial periods has sometimes been ascribed to 
this source. When tropical life flourished around 
the poles, as the remains in the rocks assure us, the 
needed high temperature may, it has been thought, 
have been derived from the presence of the earth in a 
warm region of space. Then, too, there is a certain 
interest for us in the thought of what our familiar 
planet has passed through. We cannot but admire 
it for its long journeying as we admire the traveller 
who comes to us from remote and unexplored lands, 
or as we gaze with a glow of interest upon the first 

48 



STELLAR MIGRATIONS 

locomotive that has crossed a continent, or a ship 
that has visited the Arctic or Antarctic regions. If 
we may trust the indications of its present course, 
the earth, piloted by the sun, has come from the 
Milky Way in the far south and may eventually rejoin 
that mighty band of stars in the far north. 

While the stars in general appear to travel inde- 
pendently of one another, except when they are 
combined in binary or trinary systems, there are 
notable exceptions to this rule. In some quarters of 
the sky we behold veritable migrations of entire 
groups of stars whose members are too widely sepa- 
rated to show any indications of revolution about a 
common centre of gravity. This leads us back again 
to the wonderful group of the Pleiades. All of the 
principal stars composing that group are travelling in 
virtually parallel lines. Whatever force set them 
going evidently acted upon all alike. This might be 
explained by the assumption that when the original 
projective force acted upon them they were more 
closely united than they are at present, and that in 
drifting apart they have not lost the impulse of the 
primal motion. Or it may be supposed that they are 
carried along by some current in space, although it 
would be exceeding difficult, in the present state of 
our knowledge, to explain the nature of such a current. 
Yet the theory of a current has been proposed. As 
to an attractive centre around which they might 
revolve, none has been found. Another instance of 
similar "star-drift" is furnished by five of the seven 
stars constituting the figure of the ''Great Dipper." 
In this case the stars concerned are separated very 

49 



CURIOSITIES OF THE SKY 

widely, the two extreme ones by not less than fifteen 
degrees, so that the idea of a common motion would 
never have been suggested by their aspect in the sky; 
and the case becomes the more remarkable from the 
fact that among and between them there are other 
stars, some of the same magnitude, which do not share 
their motion, but are travelling in other directions. 
Still other examples of the same phenomenon are 
found in other parts of the sky. Of course, in the case 
of compact star-clusters, it is assumed that all the 
members share a like motion of translation through 
space, and the same is probably true of dense star- 
swarms and star-clouds. 

The whole question of star-drift has lately assumed 
a new phase, inconsequence of the investigations of 
Kapteyn, Dyson, and Eddington on the ''systematic 
motions of the stars." This research will, it is hoped, 
lead to an understanding of the general law governing 
the movements of the whole body of stars constituting 
the visible universe. Taking about eleven hundred 
stars whose proper motions have been ascertained 
with an approach to certainty, and which are dis- 
tributed in all parts of the sky, it has been shown 
that there exists an apparent double drift, in two in- 
dependent streams, moving in different and nearly 
opposed directions. The apex of the motion of what 
is called ''Stream I " is situated, according to Professor 
Kapteyn, in right ascension 85°, declination south 
11°, which places it just south of the constellation 
Orion; while the apex of "Stream II" is in right 
ascension 260°, declination south 48^, placing it in 
the constellation Ara, south of Scorpio. The two 

50 



STELLAR MIGRATIONS 

apices differ very nearly i8o° in right ascension and 
about 120° in declination. The discovery of these 
vast star-streams, if they really exist, is one of the 
most extraordinary in modern astronomy. It offers 
the correlation of stellar movements needed as the 
basis of a theory of those movements, but it seems 
far from revealing a physical cause for them. As 
projected against the celestial sphere the stars form- 
ing the two opposite streams appear intermingled, 
some obeying one tendency and some the other. As 
Professor Dyson has said, the hypothesis of this double 
movement is of a revolutionary character, and calls 
for further investigation. Indeed, it seems at first 
glance not less surprising than would be the observa- 
tion that in a snow-storm the flakes over our heads 
were divided into two parties and driving across each 
other's course in nearly opposite directions, as if 
urged by interpenetrating winds. 

But whatever explanation may eventually be found 
for the motions of the stars, the knowledge of the 
existence of those motions must always afford a new 
charm to the contemplative observer of the heavens, 
for they impart a sense of life to the starry system 
that would otherwise be lacking. A stagnant universe, 
with every star fixed immovably in its place, would 
not content the imagination or satisfy our longing 
for ceaseless activity. The majestic grandeur of the 
evolutions of the celestial hosts, the inconceivable 
vastness of the fields of space in which they are 
executed, the countless numbers, the immeasurable 
distances, the involved convolutions, the flocking 
and the scattering, the interpenetrating marches and 

51 



CURIOSITIES OF THE SKY 

countermarches, the strange community of impulsion 
affecting stars that are wide apart in space and caus- 
ing them to traverse the general movement about 
them like aides and despatch-bearers on a battle- 
field — all these arouse an intensity of interest which is 
heightened by the mystery behind them. 



IV 

THE PASSING OF THE CONSTELLATIONS 

FROM a historical and picturesque point of view, 
one of the most striking results of the motions 
of the stars described in the last chapter is their effect 
upon the forms of the constellations, which have been 
watched and admired by mankind from a period so 
early that the date of their invention is now unknown. 
The constellations are formed by chance combina- 
tions of conspicious stars, like figures in a kaleidoscope, 
and if our lives were commensurate with the seons of 
cosmic existence we should perceive that the kaleido- 
scope of the heavens was ceaselessly turning and throw- 
ing the stars into new symmetries. Even if the stars 
stood fast, the motion of the solar system would 
gradually alter the configurations, as the elements of 
a landscape dissolve and recombine in fresh group- 
ings with the traveller's progress amid them. But 
with the stars themselves all in motion at various 
speeds and in many directions, the changes occur more 
rapidly. Of course, "rapid" is here to be understood 
in a relative sense ; the wheel of human history to an 
eye accustomed to the majestic progression of the 
universe would appear to revolve with the velocity 
of a whirling dynamo. Only the deliberation of geo- 

53 



CURIOSITIES OF THE SKY^ 

logical movements can be contrasted with the evolu- 
tion and devolution of the constellations. 

And yet this secular fluctuation of the constellation 
figures is not without keen interest for the meditative 
observer. It is another reminder of the swift muta- 
bility of terrestrial affairs. To the passing glance, 
which is all that we can bestow upon these figures, they 
appear so immutable that they have been called into 
service to form the most lasting records of ancient 
thought and imagination that we possess. In the 
forms of the constellations, the most beautiful, and, in 
imaginative quality, the finest, mythology that the 
world has ever known has been perpetuated. Yet, in 
a broad sense, this scroll of human thought imprinted 
on the heavens is as evanescent as the summer clouds. 
Although more enduring than parchment, tombs, 
pyramids, and temples, it is as far as they from truly 
eternizing the memory of what man has fancied and 
done. 

Before studying the effects that the motions of the 
stars have had and will have upon the constellations, 
it is worth while to consider a little further the im- 
portance of the stellar pictures as archives of history. 
To emphasize the importance of these effects it is only 
necessary to recall that the constellations register 
the oldest traditions of our race. In the history of 
primeval religions they are the most valuable of docu- 
ments. Leaving out of account for the moment the 
more familiar mythology of the Greeks, based on 
something older yet, we may refer for illustration to 
that of the mysterious Maya race of America. At 
Izamal, in Yucatan, says Mr. Stansbury Hagar, is 

54 



PASSING OF THE CONSTELLATIONS 

a group of ruins perched, after the Mexican and 
Central- American plan, on the summits of pyramidal 
mounds which mark the site of an ancient theogonic 
centre of the Mayas. Here the temples all evi- 
dently refer to a cult based upon the constellations as 
symbols. The figures and the names, of course, were 
not the same as those that we have derived from our 
Aryan ancestors, but the star groups were the same 
or nearly so. For instance, the loftiest of the temples 
at Izamal was connected with the sign of the con- 
stellation known to us as Cancer, marking the place 
of the sun at the summer solstice, at which period the 
sun was supposed to descend at noon like a great bird 
of fire and consume the offerings left upon the altar. 
Our Scorpio was known to the Mayas as the sign of 
the ''Death God." Our Libra, the ''Balance," with 
which the idea of a divine weighing out of justice has 
always been connected, seems to be identical with the 
Mayan constellation Teoyaotlatohua with which was 
associated a temple where dwelt the priests whose 
special business it was to administer justice and to 
foretell the future by means of information obtained 
from the spirits of the dead. Orion, the "Hunter" 
of our celestial mythology, was among the Mayas a 
"Warrior," while Sagittarius and others of our con- 
stellations were known to them (under different names, 
of course), and all were endowed with a religious 
symbolism. And the same star figures, having the 
same significance, were familiar to the Peruvians, as 
shown by the temples at Cuzco. Thus the imagina- 
tion of ancient America sought in the constellations 
symbols of the unchanging gods. 
^ 55 



CURIOSITIES OF THE SKY 

But, in fact, there is no nation and no people that 
has not recognized the constellations, and at one 
period or another in its history employed them in 
some symbolic or representative capacity. As han- 
dled by the Greeks from prehistoric times, the con- 
stellation myths became the very soul of poetry. The 
imagination of that wonderful race idealized the 
principal star groups so effectively that the figures 
and traditions thus attached to them have, for civil- 
ized mankind, displaced all others, just as Greek art 
in its highest forms stands without parallel and 
eclipses every rival. The Romans translated no 
heroes and heroines of the mythical period of their 
history to the sky, and the deified Cassars never en- 
tered that lofty company, but the heavens are filled 
with the early myths of the Greeks. Herakles nightly 
resumes his mighty labors in the stars; Zeus, in the 
form of the white "Bull," Taurus, bears the fair 
Europa on his back through the celestial waves; 
Andromeda stretches forth her shackled arms in the 
star-gemmed ether, beseeching aid ; and Perseus, in a 
blaze of diamond armor, revives his heroic deeds amid 
sparkling clouds of stellar dust. There, too, sits Queen 
Cassiopeia in her dazzling chair, while the Great 
King, Cepheus, towers gigantic over the pole. Pro- 
fessor Young has significantly remarked that a great 
number of the constellations are connected in some 
way or other with the Argonautic Expedition — ^that 
strangely fascinating legend of earliest Greek story 
which has never lost its charm for mankind. In view 
of all this, we may well congratulate ourselves that the 
constellations will outlast our time and the time of 

56 



PASSING OF THE CONSTELLATIONS 

countless generations to follow us; and yet they are 
very far from being eternal. Let us now study some 
of the effects of the stellar motions upon them. 

We begin with the familiar figure of the ** Great 
Dipper." He who has not drunk inspiration from 
its celestial bowl is not yet admitted to the circle of 
Olympus. This figure is made up of seven con- 
spicuous stars in the constellation Ursa Major, the 
"Greater Bear." The handle of the ''Dipper" cor- 
responds to the tail of the imaginary "Bear," and the 
bowl lies upon his flank. In fact, the figure of a dipper 
is so evident and that of a bear so unevident, that to 
most persons the "Great Dipper" is the only part of 
the constellation that is recognizable. Of the seven 
stars mentioned, six are of nearly equal brightness, 
ranking as of the second magnitude, while the seventh 
is of only the third magnitude. The difference is very 
striking, since every increase of one magnitude in- 
volves an increase of two-and-a-half times in bright- 
ness. There appears to be little doubt that the faint 
star, which is situated at the junction of the bowl 
and the handle, is a variable of long period, since 
three hundred years ago it was as bright as its com- 
panions. But however that may be, its relative faint- 
ness at the present time interferes but little with the 
perfection of the "Dipper's" figure. In order the 
more readily to understand the changes which are 
taking place, it will be well to mention both the names 
and the Greek letters which are attached to the seven 
stars. Beginning at the star in the upper outer edge 
of the rim of the bowl and running in regular order 
round the bottom and then out to the end of the handle, 

57 



CURIOSITIES OF THE SKY 

the names and letters are as follows: Dubhe (a), 
Merak (jS), Phaed (7), Megrez (g), Alioth (0, 
Mizar (c), and Benetnasch (v). Megrez is the faint 
star already mentioned at the junction of the bowl 
and handle, and Mizar, in the middle of the handle, has 
a close, naked-eye companion which is named Alcor. 



THE "great dipper AS IT IS 



AS IT WILL BE 



f 
AS IT WAS FORMERLY 

58 



PASSING OF THE CONSTELLATIONS 

The Arabs called this singular pair of stars ''The 
Horse and Rider." Merak and Dubhe are called 
"The Pointers," because an imaginary line drawn 
northward through them indicates the Pole Star. 

Now it has been found that five of these stars — viz. , 
Merak, Phaed, Megrez, Alioth, and Mizar (with its 
comrade) — are moving with practically the same speed 
in an easterly direction, while the other two, Dubhe 
and Benetnasch, are simultaneously moving west- 
ward, the motion of Benetnasch being apparently 
the more rapid. The consequence of these opposed 
motions is, of course, that the figure of the *' Dipper" 
cannot always have existed and will not continue to 
exist. In the accompanying diagrams it has been 
thought interesting to show the relative positions of 
these seven stars, as seen from the point which the 
earth now occupies, both in the past and in the future. 
Arrows attached to the stars in the figure representing 
the present appearance of the "Dipper" indicate the 
directions of the motions and the distances over which 
they will carry the stars in a period of about five 
hundred centuries. The time, no doubt, seems long, 
but remember the vast stretch of ages through which 
the earth has passed, and then reflect that no reason 
is apparent why our globe should not continue to be 
a scene of animation for ten thousand centuries yet 
to come. The fact that the little star Alcor placed 
so close to Mizar should accompany the latter in its 
flight is not surprising, but that two of the principal 
stars of the group should be found moving in a direc- 
tion exactly opposed to that pursued by the other five 
is surprising in the highest degree; and it recalls the 

59 



CURIOSITIES OF THE SKY 

strange theory of a double drift affecting all the stars, 
to which attention was called in the preceding chapter. 
It would appear that Benetnasch and Dubhe belong 



•^ 




CASSIOPEIA AT PRESENT 



CASSIOPEIA IN THE FUTURE 



to one ''current," and Merak, Phaed, Megrez, Alioth, 
and Mizar to the other. As far as is known, the mo- 
tions of the seven stars are not shared by the smaller 

60 



PASSING OF THE CONSTELLATIONS 

stars scattered about them, but on the theory of cur- 
rents there should be such community of motion, 
and further investigation may reveal it. 

From the ** Great Dipper" we turn to a constella- 
tion hardly less conspicuous and situated at an equal 
distance from the pole on the other side— Cassiopeia. 
This famous star-group commemorating the romantic 
Queen of Ethiopia whose vain boasting of her beauty 
was punished by the exposure of her daughter 
Andromeda to the ''Sea Monster," is well marked 
by five stars which form an irregular letter "W" 
with its open side toward the pole. Three of these 
stars are usually ranked as of the second magnitude, 
and two of the third; but to ordinary observation 
they appear of nearly equal brightness, and present 
a very striking picture. They mark out the chair 
and a part of the figure of the beautiful queen. Be- 
ginning at the right-hand, or western, end of the 
"W," their Greek letter designations are: Beta (j3). 
Alpha (a), Gamma (y). Delta (^), and Epsilon (g). 
Four of them. Beta, Alpha, Delta, and Epsilon are 
travelling eastwardly at various speeds, while the fifth. 
Gamma, moves in a westerly direction. The motion 
of Beta is more rapid than that of any of the others. 
It should be said, however, that no little uncertainty 
attaches to the estimates of the rate of motion of 
stars which are not going very rapidly, and different 
observers often vary considerably in their results. 

In the beautiful ''Northern Crown," one of the 
most perfect and charming of all the figures to be 
found in the stars, the alternate combining and 
scattering effects of the stellar motions are shown by 

6i 



CURIOSITIES OF THE SKY 

comparing the appearance which the constellation 
must have had five hundred centuries ago with that 
which it has at present and that which it will have 
in the future. The seven principal stars of the 
asterism, forming a surprisingly perfect coronet, have 
movements in three directions at right angles to one 
another. That in these circumstances they should 
ever have arrived at positions giving them so striking 
an appearance of definite association is certainly 
surprising; from its aspect one would have expected 
to find a community of movement governing the 
brilliants of the "Crown," but instead of that we find 
evidence that they will inevitably drift apart and the 
beautiful figure will dissolve. 

A similar fate awaits such asterisms as the ''North- 
em Cross" in Cygnus; the "Crow" (Corvus), which 
stands on the back of the great "Sea Serpent," 
Hydra, and pecks at his scales; "Job's Coffin" 
(Delphinus); the "Great Square of Pegasus"; the 
' ' Twins ' ' (Gemini) ; the beautiful ' ' Sickle ' ' in Leo ; and 
the exquisite group of the Hyades in Taurus. In the 
case of the Hyades, two controlling movements are 
manifest: one, affecting five of the stars which form 
the well-known figure of a letter "V," is directed 
northerly; the other, which controls the direction of 
two stars, has an easterly trend. The chief star of 
the group, Aldebaran, one of the finest of all stars 
both for its brilliance and its color, is the most affect- 
ed by the easterly motion. In time it will drift en- 
tirely out of connection with its present neighbors. 
Although the Hyades do not form so compact a group 
as the Pleiades in the same constellation, yet their 

62 



PASSING OF THE CONSTELLATIONS 

appearance of relationship is sufficient to awaken a 
feeling of surprise over the fact that, as with the stars 
of the * 'Dipper," their association is only temporary or 
apparent. 





• 


% 


» 


# 


• 

• 


# 


• The 
Pearl 


• 

# Tbe Pearl 

• 


THE 


" NORTHERN CROWN " AT 


THE "NORTHERN CROWN " IN THE 




PRESENT 


FUTURE 



Tbe Pearl 



THE "NORTHERN CROWN IN THE PAST 

The great figure of Orion appears to be more last- 
ing, not because its stars are physically connected, 
but because of their great distance, which renders 

63 



CURIOSITIES OF THE SKY 

their movements too deliberate to be exactly ascer- 
tained. Two of the greatest of its stars, Betelgeuse 
and Rigel, possess, as far as has been ascertained, 
no perceptible motion across the line of sight, but 
there is a little movement perceptible in the "Belt." 
At the present time this consists of an almost perfect 
straight line, a row of second-magnitude stars about 
equally spaced and of the most striking beauty. In 
the course of time, however, the two right-hand 
stars, Mintaka and Alnilam (how fine are these Arabic 
star names!) will approach each other and form a 
naked-eye double, but the third, Alnita, will drift 
away eastward, so that the "Belt" will no longer 
exist. 

For one more example, let us go to the southern 
hemisphere, whose most celebrated constellation, 
the "Southern Cross," has found a place in all modern 
literatures, although it has no claim to consideration 
on account of association with ancient legends. This 
most attractive aster ism, which has never ceased to 
fascinate the imagination of Christendom since it was 
first devoutly described by the early explorers of the 
South, is but a passing collocation of brilliant stars. 
Yet even in its transfigurations it has been for hun- 
dreds of centuries, and will continue to be for hun- 
dreds of centuries to come, a most striking object in 
the sky. Our figures show its appearance in three 
successive phases: first, as it was fifty thousand years 
ago (viewed from the earth's present location) ; second, 
as it is in our day ; and, third, as it will be an equal time 
in the future. The nearness of these bright stars to 
one another — ^the length of the longer beam of the 

64 



PASSING OF THE CONSTELLATIONS 

"Cross" is only six degrees — ^makes this group very 
noticeable, whatever the arrangement of its com- 
ponents may be. The largest star, at the base of the 
''Cross," is of the first magnitude, two of the others 
are of the second magnitude, and the fourth is of 
the third. Other stars, not represented in the figures. 



THE ** SOUTHERN CROSS " THE " SOUTHERN CROSS " 
AS IT IS AS IT WILL BE 



THE " SOUTHERN CROSS AS IT ONCE WAS 

increase the effect of a celestial blazonry, although 
they do not help the resemblance to a cross. 

But since the motion of the solar system itself will, 
in the course of so long a period as fifty thousand 
years, produce a great change in the perspective of 
the heavens as seen from the earth, by carrying us 
nearly nineteen trillion miles from our present place, 

65 



CURIOSITIES OF THE SKY 

why, it may be asked, seek to represent future ap- 
pearances of the constellations which we could not 
hope to see, even if we could survive so long? The 
answer is : Because these things aid the mind to form 
a picture of the effects of the mobility of the starry 
universe. Only by showing the changes from some 
definite point of view can we arrive at a due com- 
prehension of them. The constellations are more or 
less familiar to everybody, so that impending changes 
of their forms must at once strike the eye and the 
imagination, and make clearer the significance of the 
movements of the stars. If the future history of 
mankind is to resemble its past and if our race is 
destined to survive yet a million years, then our 
remote descendants will see a "new heavens" if not 
a "new earth," and will have to invent novel con- 
stellations to perpetuate their legends and my- 
thologies. 

If our knowledge of the relative distances of the 
stars were more complete, it would be an interesting 
exercise in celestial geometry to project the con- 
stellations probably visible to the inhabitants of 
worlds revolving around some of the other suns of 
space. Our sun is too insignificant for us to think 
that he can make a conspicuous appearance among 
them, except, perhaps, in a few cases. As seen, 
for instance, from the nearest known star, Alpha 
Centauri, the sun would appear of the average first 
magnitude, and consequently from that standpoint 
he might be the gem of some little constellation which 
had no Sirius, or Arcturus, or Vega to eclipse him with 
its superior splendor. But from the distance of the 

66 



PASSING OF THE CONSTELLATIONS 

vast majority of the stars the sun would probably be 
invisible to the naked eye, and as seen from nearer 
systems could only rank as a fifth or sixth magnitude 
star, unnoticed and unknown except by the star- 
charting astronomer. 



V 

CONFLAGRATIONS IN THE HEAVENS 

SUPPOSE it were possible for the world to take 
fire and burn up — as some pessimists think that 
it will do when the Divine wrath shall have sufficiently 
accumulated against it — nobody out of our own little 
corner of space would ever be aware of the catastrophe ! 
With all their telescopes, the astronomers living in the 
golden light of Arcturus or the diamond blaze of 
Canopus would be unable to detect the least glimmer 
of the conflagration that had destroyed the seat of 
Adam and his descendants, just as now they are 
totally ignorant of its existence. 

But at least fifteen times in the course of recorded 
history men looking out from the earth have beheld 
in the remote depths of space great outbursts of fiery 
light, some of them more splendidly luminous than 
anything else in the firmament except the sun! If 
they were conflagrations, how many million worlds 
like ours were required to feed their blaze ? 

It is probable that ''temporary" or "new" stars, 
as these wonderful apparitions are called, really are 
conflagrations ; not in the sense of a bonfire or a burn- 
ing house or city, but in that of a sudden eruption of 
inconceivable heat and hght, such as would result 

68 



CONFLAGRATIONS 

from the stripping off the shell of an encrusted sun 
or the crashing together of two mighty orbs flying 
through space with a hundred times the velocity of 
the swiftest cannon-shot. 

Temporary stars are the rarest and most erratic 
of astronomical phenomena. The earliest records 
relating to them are not very clear, and we cannot in 
every instance be certain that it was one of these 
appearances that the ignorant and superstitious old 
chroniclers are trying to describe. The first tem- 
porary star that we are absolutely sure of appeared 
in 1572, and is known as "Tycho's Star," because the 
celebrated Danish astronomer (whose remains, with 
his gold-and-silver artificial nose — made necessary 
by a duel — still intact, were disinterred and reburied 
in 1 901) was the first to perceive it in the sky, and the 
most assiduous and successful in his studies of it. 
As the first fully accredited representative of its class, 
this new star made its entry upon the scene with 
becoming eclat. It is characteristic of these phenom- 
ena that they burst into view with amazing sudden- 
ness, and, of course, entirely unexpectedly. Tycho's 
star appeared in the constellation Cassiopeia, near 
a now well-known and much- watched little star named 
Kappa, on the evening of November 11, 1572. The 
story has often been repeated, but it never loses in- 
terest, how Tycho, going home that evening, saw 
people in the street pointing and staring at the 
sky directly over their heads, and following the direc- 
tion of their hands and eyes he was astonished to see, 
near the zenith, an unknown star of surpassing brill- 
iance. It outshone the planet Jupiter, and was there- 

69 



CURIOSITIES OF THE SKY 

fore far brighter than the first magnitude. There was 
not another star in the heavens that could be compared 
with it in splendor. Tycho was not in all respects free 
from the superstitions of his time — and who is ? — but 
he had the true scientific instinct, and immediately he 
began to study the stranger, and to record with the 
greatest care every change in its aspect. First he de- 
termined as well as he could with the imperfect in- 
struments of his day, many of which he had himself 
invented, the precise location of the phenomenon in 
the sky. Then he followed the changes that it under- 
went. At first it brightened until its light equalled 
or exceeded that of the planet Venus at her bright- 
est, a statement which will be appreciated at its full 
value by any one who has ever watched Venus when 
she plays her dazzling role of ''Evening Star," flaring 
like an arc Hght in the sunset sky. It even became 
so brilliant as to be visible in full daylight, since, its 
position being circumpolar, it never set in the latitude 
of Northern Europe. Finally it began to fade, turn- 
ing red as it did so, and in March, 1574, it disappeared 
from Tycho 's searching gaze, and has never been seen 
again from that day to this. None of the astronomers 
of the time could make anything of it. They had not 
yet as many bases of speculation as we possess to-day. 
Tycho 's star has achieved a romantic reputation by 
being fancifully identified with the "Star of Bethle- 
hem," said to have led the wondering Magi from their 
eastern deserts to the cradle-manger of the Savior in 
Palestine. Many attempts have been made to 
connect this traditional *'star" with some known 
phenomenon of the heavens, and none seems more 

70 



Co 
«> 

\ \ • 



\ 
\ 
\ 
\ 
\ 
\ 






/ 

\ Camelopardalis / 






c. 



• P \ ^ • / -^^ Cepheus .^ 

I ' •r ... N. 






- -^-^^^ 



/ - •/< ^^ 



X - 






/ Perseus •<> •o- • \ . 

/ ^ • \ Cassiopeia 

• ,.^1- . Algol ^. • ->.^^^ 



CHART SHOWING LOCATION OF TYCHO's STAR, 1572, AND NOVA 

PERSEI OF 19OI 



CONFLAGRATIONS 

idle than this. Yet it persistently survives, and no 
astronomer is free from eager questions about it ad- 
dressed by people whose imagination has been excited 
by the legend. It is only necessary to say that the 
supposition of a connection between the phenomenon 
of the Magi and Tycho's star is without any scien- 
tific foundation. It was originally based upon an 
unwarranted assumption that the star of Tycho was 
a variable of long period, appearing once every three 
hundred and fifteen years, or thereabout. If that 
were true there would have been an apparition some- 
where near the traditional date of the birth of Christ, 
a date which is itself uncertain. But even the data 
on which the assumption was based are inconsistent 
with the theory. Certain monkish records speak of 
something wonderful appearing in the sky in the years 
1264 and 945, and these were taken to have been 
outbursts of Tycho's star. Investigation shows that 
the records more probably refer to comets, but even 
if the objects seen were temporary stars, their dates 
do not suit the hypothesis; from 945 to 1264 there is 
a gap of 319 years, and from 1264 to 1572 one of only 
308 years; moreover, 337 years have now (1909) 
elapsed since Tycho saw the last glimmer of his star. 
Upon a variability so irregular and uncertain as that, 
even if we felt sure that it existed, no conclusion could 
be found concerning an apparition occurring 2000 
years ago. 

In the year 1600 (the year in which Giordano Bruno 

was burned at the stake for teaching that there is 

more than one physical world) , a temporary star of the 

third magnitude broke out in the constellation Cygnus, 

' 73 



CURIOSITIES OF THE SKY 

and curiously enough, considering the rarity of such 
phenomena, only four years later another surprisingly 
brilliant one appeared in the constellation Ophiuchus. 
This is often called ''Kepler's Star," because the great 
German astronomer devoted to it the same attention 
that Tycho had given to the earlier phenomenon. 
It, too, like Tycho's, was at first the brightest object 
in the stellar heavens, although it seems never to have 
quite equalled its famous predecessor in splendor. 
It disappeared after a year, also turning of a red color 
as it became more faint. We shall see the significance 
of this as we go on. Some of Kepler's contemporaries 
suggested that the outburst of this star was due to a 
meeting of atoms in space, an idea bearing a striking 
resemblance to the modem theory of "astronomical 
collisions.'* 

In 1670, 1848, and i860 temporary stars made their 
appearance, but none of them was of great brilliance. 
In 1866 one of the second magnitude broke forth in 
the "Northern Crown" and awoke much interest, 
because by that time the spectroscope had begun 
to be employed in studying the composition of the 
stars, and Huggins demonstrated that the new star 
consisted largely of incandescent hydrogen. But 
this star, apparently unlike the others mentioned, was 
not absolutely new. Before its outburst it had shone 
as a star of the ninth magnitude (entirely invisible, 
of course, to the naked eye), and after about six weeks 
it faded to its original condition in which it has 
ever since remained. In 1876 a temporary star ap- 
peared in the constellation Cygnus, and attained at 
one time the brightness of the second magnitude. 

74 



CONFLAGRATIONS 

Its spectrum and its behavior resembled those of its 
immediate predecessor. In 1885 astronomers were 
surprised to see a sixth-magnitude star gliinmering 
in the midst of the hazy cloud of the great Andromeda 
Nebula. It soon absolutely disappeared. Its spec- 
trum was remarkable for being ''continuous, " like 
that of the nebula itself. A continuous spectrum is 
supposed to represent a body, or a mass, which is 
either solid or liquid, or composed of gas under great 
pressure. In January, 1892, a new star was suddenly 
seen in the constellation Auriga. It never rose much 
above the fourth magnitude, but it showed a peculiar 
spectrum containing both bright and dark lines of 
hydrogen. 

But a bewildering surprise was now in store; the 
world was to behold at the opening of the twentieth 
century such a celestial spectacle as had not been on 
view since the times of Tycho and Kepler. Before 
daylight on the morning of February 22, 1901, the 
Rev. Doctor Anderson, of Edinburgh, an amateur 
astronomer, who had also been the first to see the new 
star in Auriga, beheld a strange object in the con- 
stellation Perseus not far from the celebrated variable 
star Algol. He recognized its character at once, and 
immediately telegraphed the news, which awoke the 
startled attention of astronomers all over the world. 
When first seen the new star was no brighter than 
Algol (less than the second magnitude), but within 
twenty- four hours it was ablaze, outshining even the 
brilliant Capella, and far surpassing the first magni- 
tude. At the spot in the sky where it appeared noth- 
ing whatever was visible on the night before its com- 

75 



CURIOSITIES OF THE SKY 

ing. This is known with certainty because a photo- 
graph had been made of that very region on Feb- 
ruary 21, and this photograph showed everything 
down to the twelfth magnitude, but not a trace of the 
stranger which burst into view between the 21st and 
the 2 2d Hke the explosion of a rocket. 

Upon one who knew the stars the apparition of this 
intruder in a well-known constellation had the effect 
of a sudden invasion. The new star was not far west 
of the zenith in the early evening, and in that position 
showed to the best advantage. To see Capella, the 
hitherto unchallenged ruler of that quarter of the 
sky, abased by comparison with this stranger of alien 
aspect, for there was always an unfamiliar look about 
the "nova," was decidedly disconcerting. It seemed 
to portend the beginning of a revolution in the heavens. 
One could understand what the effect of such an 
apparition must have been in the superstitious times 
of Tycho. The star of Tycho had burst forth on the 
northern border of the Milky Way; this one was on 
its southern border, some forty-five degrees farther 
east. 

Astronomers were well prepared this time for the 
scientific study of the new star, both astronomical 
photography and spectroscopy having been perfected, 
and the results of their investigations were calculated 
to increase the wonder with which the phenomenon 
was regarded. The star remained at its brightest 
only a few days ; then, like a veritable conflagration, it 
began to languish ; and, like the reflection of a dying 
fire, as it sank it began to glow with the red color of 
embers. But its changes were spasmodic ; once about 

76 



CONFLAGRATIONS 

every three days it flared up only to die away again. 
During these fluctuations its light varied alternately 
in the ratio of one to six. Finally it took a permanent 
downward course, and after a few months the naked 
eye could no longer perceive it; but it remained 
visible with telescopes, gradually fading until it had 
sunk to the ninth magnitude. Then another as- 
tonishing change happened: in August photographs 
taken at the Yerkes Observatory and at Heidelberg 
showed that the ''nova" was surrounded by a spiral 
nebula! The nebula had not been there before, 
and no one could doubt that it represented a phase 
of the same catastrophe that had produced the out- 
burst of the new star. At one time the star seemed 
virtually to have disappeared, as if all its substance 
had been expanded into the nebulous cloud, but 
always there remained a stellar nucleus about which 
the misty spiral spread wider and ever wider, like a 
wave expanding around a centre of disturbance. The 
nebula too showed a variability of brightness, and four 
condensations which formed in it seemed to have a 
motion of revolution about the star. As time went 
on the nebula continued to expand at a rate which 
was computed to be not less than twenty thousand 
miles per second! And now the star itself, showing 
indications of having turned into a nebula, behaved 
in a most erratic manner, giving rise to the suspicion 
that it was about to burst out again. But this did 
not occur, and at length it sunk into a state of lethargy 
from which it has to the present time not recovered. 
But the nebulous spiral has disappeared, and the 
entire phenomenon as it now (1909) exists consists 

77 



CURIOSITIES OF THE SKY 

of a faint nebulous star of less than the ninth magni- 
tude. 

The wonderful transformations just described had 
been forecast in advance of the discovery of the 
nebulous spiral encircling the star by the spectro- 
scopic study of the latter. At first there was no sug- 
gestion of a nebular constitution, but within a month 
or two characteristic nebular lines began to appear, 
and in less than six months the whole spectrum had 
been transformed to the nebular type. In the mean 
time the shifting of the spectral lines indicated a com- 
plication of rapid motions in several directions simul- 
taneously. These motions were estimated to amount 
to from one hundred to five hundred miles per second. 

The human mind is so constituted that it feels 
forced to seek an explanation of so marvellous a« 
phenomenon as this, even in the absence of the data 
needed for a sound conclusion. The most natural 
hypothesis, perhaps, is that of a collision. Such a 
catastrophe could certainly happen. It has been 
shown, for instance, that in infinity of time the earth 
is sure to be hit by a comet ; in the same way it may 
be asserted that, if no time limit is fixed, the sun is 
certain to run against some obstacle in space, either 
another star, or a dense meteor swarm, or one of the 
dark bodies which there is every reason to believe 
abound around us. The consequences of such a 
collision are easy to foretell, provided that we know 
the masses and the velocities of the colliding bodies. 
In a preceding chapter we have discussed the motions 
of the sun and stars, and have seen that they are so 
swift that an encounter between any two of them 

78 



CONFLAGRATIONS 

could not but be disastrous. But this is not all; 
for as soon as two stars approached within a few 
million miles their speed would be enormously in- 
creased by their reciprocal attractions and, if their 
motion was directed radially with respect to their 
centres, they would come together with a crash that 
would reduce them both to nebulous clouds. It is 
true that the chances of such a "head-on" collision 
are relatively very small; two stars approaching each 
other would most probably fall into closed orbits 
around their common centre of gravity. If there 
were a collision it would most likely be a grazing one 
instead of a direct front-to-front encounter. But 
even a close approach, without any actual collision, 
would probably prove disastrous, owing to the tidal 
• influence of each of the bodies upon the other. Suns, 
in consequence of their enormous masses and di- 
mensions and the peculiarities of their constitution, 
are exceedingly dangerous to one another at close 
quarters. Propinquity awakes in them a mutually 
destructive tendency. Consisting of matter in the 
gaseous, or perhaps, in some cases, liquid, state, their 
tidal pull upon each other if brought close together 
might burst them asunder, and the photospheric 
envelope being destroyed the internal incandescent 
mass would gush out, bringing fiery death to any 
planets that were revolving near. Without regard 
to the resulting disturbance of the earth's orbit, the 
close approach of a great star to the sun would be in 
the highest degree perilous to us. But this is a danger 
which may properly be regarded as indefinitely re- 
mote, since, at our present location in space, we are 

79 



CURIOSITIES OF THE SKY 

certainly far from every star except the sun, and we 
may feel confident that no great invisible body is 
near, for if there were one we should be aware of its 
presence from the effects of its attraction. As to 
dark nebulas which may possibly lie in the track that 
the solar system is pursuing at the rate of 375,000,000 
miles per year, that is another question— and they, too, 
could be dangerous! 

This brings us directly back to ''Nova Persi," for 
among the many suggestions offered to explain its 
outburst, as well as those of other temporary stars, 
one of the most fruitful is that of a collision between 
a star and a vast invisible nebula. Professor Seeliger, 
of Munich, first proposed this theory, but it afterward 
underwent some modifications from others. Stated 
in a general form, the idea is that a huge dark body, 
perhaps an extinguished sun, encountered in its 
progress through space a widespread flock of small 
meteors forming a dark nebula. As it plunged into 
the swarm the friction of the innumerable collisions 
with the meteors heated its surface to incandescence, 
and being of vast size it then became visible to us as a 
new star. Meanwhile the motion of the body through 
the nebula, and its rotation upon itself, set up a 
gyration in the blazing atmosphere formed around it 
by the vaporized meteors; and as this atmosphere 
spread wider, under the laws of gyratory motion a 
rotation in the opposite direction began in the in- 
flamed meteoric cloud outside the central part of the 
vortex. Thus the spectral lines were caused to show 
motion in opposite directions, a part of the incan- 
descent mass approaching the earth simultaneously 

80 



o 

en 






H 

w 

C! 
> 

fa 
o 




CONFLAGRATIONS 

with the retreat of another part. So the curious 
spectroscopic observations before mentioned were ex- 
plained. This theory might also account for the 
appearance of the nebulous spiral first seen some six 
months after the original outburst. The sequent 
changes in the spectrum of the **nova" are accounted 
for by this theory on the assumption, reasonable 
enough in itself, that at first the invading body would 
be enveloped in a vaporized atmosphere of relatively 
slight depth, producing by its absorption the fine 
dark lines first observed' but that as time went on 
and the incessant collisions continued, the blazing 
atmosphere would become very deep and extensive, 
whereupon the appearance of the spectral lines would 
change, and bright lines due to the light of the in- 
candescent meteors surrounding the nucleus at a 
great distance would take the place of the original 
dark ones. The vortex of meteors once formed 
would protect the flying body within from further 
immediate collisions, the latter now occurring mainly 
among the meteors themselves, and then the central 
blaze would die down, and the original splendor of the 
phenomenon would fade. 

But the theories about Nova Persei have been 
almost as numerous as the astronomers who have 
speculated about it. One of the most startling of 
them assumed that the outburst was caused by the 
running amuck of a dark star which had encountered 
another star surrounded with planets, the renewed 
outbreaks of light after the principal one had faded 
being due to the successive running down of the un- 
fortunate planets! Yet another hypothesis is based 

83 



CURIOSITIES OF THE SKY 

on what we have already said of the tidal influence 
that two close approaching suns would have upon 
each other. Supposing two such bodies which had 
become encrusted, but remained incandescent and 
fluid within, to approach within almost striking dis- 
tance; they would whirl each other about their com- 
mon centre of gravity, and at the same time their 
shells would burst under the tidal strain, and their 
glowing nuclei being disclosed would produce a great 
outburst of light. Applying this theory to a "nova," 
like that of 1866 in the "Northern Crown," which 
had been visible as a small star before the outbreak, 
and which afterward resumed its former aspect, we 
should have to assume that a yet shining sun had 
been approached by a dark body whose attraction 
temporarily burst open its photosphere. It might 
be supposed that in this case the dark body was too 
far advanced in cooling to suffer the same fate from 
the tidal pull of its victim. But a close approach of 
that kind would be expected to result in the forma- 
tion of a binary system, with orbits of great eccentri- 
city, perhaps, and after the lapse of a certain time the 
outburst should be renewed by another approxima- 
tion of the two bodies. A temporary star of that 
kind would rather be ranked as a variable. 

The celebrated French astronomer, Janssen, had a 
different theory of Nova Persei, and of temporary 
stars in general. According to his idea, such phe- 
nomena might be the result of chemical changes 
taking place in a sun without interference by, or 
collision with, another body. Janssen was engaged 
for many years in trying to discover evidence of the 

84 



CONFLAGRATIONS 

existence of oxygen in the sun, and he constructed his 
observatory on the summit of Mont Blanc specially 
to pursue that research. He believed that oxygen 
must surely exist in the sun since we find so many other 
familiar elements included in the constitution of the 
solar globe, and as he was unable to discover satis- 
factory evidence of its presence he assumed that it 
existed there in a form unknown on the earth. If 
it were normally in the sun's chromosphere, or 
coronal atmosphere, he said, it would combine with 
the hydrogen which we know is there and form an 
obscuring envelope of water vapor. It exists, then, 
in a special state, uncombined with hydrogen; but 
let the temperature of the sun sink to a critical point 
and the oxygen will assume its normal properties and 
combine with the hydrogen, producing a mighty out- 
burst of light and heat. This, Janssen thought, 
might explain the phenomena of the temporary stars. 
It would also, he suggested, account for their brief 
career, because the combination of the elements would 
be quickly accomplished, and then the resulting water 
vapor would form an atmosphere cutting off the 
radiation from the star within. 

This theory may be said to have a livelier human 
interest than some of the others, since, according to it, 
the sun may carry in its very constitution a menace 
to mankind ; one does not like to think of it being sud- 
denly transformed into a gigantic laboratory for the 
explosive combination of oxygen and hydrogen! 
But while Janssen' s theory might do for some tem- 
porary stars, it is inadequate to explain all the 
phenomena of Nova Persei, and particularly the 

85 



CURIOSITIES OF THE SKY 

appearance of the great spiral nebula that seemed to 
exhale from the heart of the star. Upon the whole, 
the theory of an encounter between a star and a dark 
nebula seems best to fit the observations. By that 
hypothesis the expanding billow of light surrounding 
the core of the conflagration is very well accounted 
for, and the spectroscopic peculiarities are also ex- 
plained. 

Dr. Gustav Le Bon offers a yet more alarming 
theory, suggesting that temporary stars are the 
result of atomic explosion; but we shall touch upon 
this more fully in Chapter XIV. 

Twice in the course of this discussion we have 
called attention to the change of color invariably 
undergone by temporary stars in the later stages of 
their career. This was conspicuous with Nova 
Persei which glowed more and more redly as it faded, 
until the nebulous light began to overpower that of 
the stellar nucleus. Nothing could be more sugges- 
tive of the dying out of a great fire. Moreover, 
change of color from white to red is characteristic of 
all variable stars of long period, such as ''Mira" in 
Cetus. It is also characteristic of stars believed to 
be in the later stages of evolution, and consequently 
approaching extinction, like Antares and Betelgeuse, 
and still more notably certain small stars which 
"gleam like rubies in the field of the telescope." 
These last appear to be suns in the closing period of 
existence as self-luminous bodies. Between the white 
stars, such as Sirius and Rigel, and the red stars, such 
as Aldebaran and Alpha Herculis, there is a pro- 
gressive series of colors from golden yellow through 

86 



CONFLAGRATIONS 

orange to deep red. The change is beHeved to be due 
to the increase of absorbing vapors in the stellar 
atmosphere as the body cools down. In the case of 
ordinary stars these changes no doubt occupy many 
millions of years, which represent the average dura- 
tion of solar life ; but the temporary stars run through 
similar changes in a few months: they resemble 
ephemeral insects — born in the morning and doomed 
to perish with the going down of the sun. 



VI 

EXPLOSIVE AND WHIRLING NEBULAE 

ONE of the most surprising triumphs of celestial 
photography was Professor Keeler's discovery, 
in 1899, that the great majority of the nebulas have a 
distinctly spiral form. This form, previously known 
in Lord Rosse's great "Whirlpool Nebula," had been 
supposed to be exceptional; now the photographs, 
far excelling telescopic views in the revelation of 
nebular forms, showed the spiral to be the typical 
shape. Indeed, it is a question whether all nebulae are 
not to some extent spiral. The extreme importance 
of this discovery is shown in the effect that it has had 
upon hitherto prevailing views of solar and planetary 
evolution. For more than three-quarters of a century 
Laplace's celebrated hypothesis of the manner of 
origin of the solar system from a rotating and con- 
tracting nebula surrounding the sun had guided 
speculation on that subject, and had been tentatively 
extended to cover the evolution of systems in general. 
The apparent forms of some of the nebulae which the 
telescope had revealed were regarded, and by some 
are still regarded, as giving visual evidence in favor 
of this theory. There is a "ring nebula" in Lyra 
with a central star, and a "planetary nebula" in 

88 




LORD ROSSE's nebula 



WHIRLING NEBULA 

Gemini bearing no little resemblance to the planet 
Saturn with its rings, both of which appear to be 
practical realizations of Laplace's idea, and the 
elliptical rings surrounding the central condensation 
of the Andromeda Nebula may be cited for the same 
kind of proof. 

But since Keeler's discovery there has been a de- 
cided turning of speculation another way. The form 
of the spiral nebula seems to be entirely inconsistent 
with the theory of an originally globular or disk- 
shaped nebula condensing around a sun and throw- 
ing or leaving off rings, to be subsequently shaped 
into planets. Some astronomers, indeed, now reject 
Laplace's hypothesis in toto, preferring to think that 
even our solar system originated from a spiral nebula. 
Since the spiral type prevails among the existing 
nebula, we must make any mechanical theory of the 
development of stars and planetary systems from 
them accord with the requirements which that form 
imposes. A glance at the extraordinary variations 
upon the spiral which Professor Keeler's photographs 
reveal is sufficient to convince one of the difficulty 
of the task of basing a general theory upon them. In 
truth, it is much easier to criticize Laplace's hypothesis 
than to invent a satisfactory substitute for it. If the 
spiral nebulas seem to oppose it there are other nebulse 
which appear to support it, and it may be that no one 
fixed theory can account for all the forms of stellar 
evolution in the universe. Our particular planetary 
system may have originated very much as the great 
French mathematician supposed, while others have 
undergone, or are now undergoing, a different process 

91 



CURIOSITIES OF THE SKY 

of development. There is always a too strong 
tendency to regard an important new discovery and 
the theories and speculations based upon it as revolu- 
tionizing knowledge, and displacing or overthrowing 
everything that went before. Upon the plea that 
** Laplace only made a guess" more recent guesses 
have been driven to extremes and treated by in- 
judicious exponents as ''the solid facts at last." 

Before considering more recent theories than La- 
place's, let us see what the nature of the photographic 
revelations is. The vast celestial maelstrom dis- 
covered by Lord Rosse in the "Hunting Dogs" may 
be taken as the leading type of the spiral nebulae, 
although there are less conspicuous objects of the kind 
which, perhaps, better illustrate some of their pe- 
culiarities. Lord Rosse's nebula appears far more 
wonderful in the photographs than in his drawings 
made with the aid of his giant reflecting telescope at 
Parsonstown, for the photographic plate records 
details that no telescope is capable of showing. 
Suppose we look at the photograph of this object as 
any person of common sense would look at any great 
and strange natural phenomenon. What is the first 
thing that strikes the mind ? It is certainly the ap- 
pearance of violent whirling motion.. One would say 
that the whole glowing mass had been spun about with 
tremendous velocity, or that it had been set rotating 
so rapidly that it had become the victim of "centrif- 
ugal force," one huge fragment having broken loose 
and started to gyrate off into space. Closer inspec- 
tion shows that in addition to the principal focus 
there are various smaller condensations scattered 

92 




WONDERFUL SPIRAL IN TRIANGULUM 



WHIRLING NEBULA 

through the mass. These are conspicuous in the 
spirals. Some of them are stellar points, and but for 
the significance of their location we might suppose 
them to be stars which happen to lie in line between 
us and the nebula. But when we observe how many 
of them follow most faithfully the curves of the 
spirals we cannot but conclude that they form an 
essential part of the phenomenon; it is not possible 
to believe that their presence in such situations is 
merely fortuitous. One of the outer spirals has at 
least a dozen of these star-like points strung upon it ; 
some of them sharp, small, and distinct, others more 
blurred and nebulous, suggesting different stages of 
condensation. Even the part which seems to have 
been flung loose from the main mass has, in addition 
to its central condensation, at least one stellar point 
gleaming in the half-vanished spire attached to 
it. Some of the more distant stars scattered around 
the "whirlpool" look as if they too had been shot out 
of the mighty vortex, afterward condensing into un- 
mistakable solar bodies. There are at least two 
curved rows of minute stars a little beyond the 
periphery of the luminous whorl which clearly follow 
lines concentric with those of the nebulous spirals. 
Such facts are simply dumfounding for any one who 
will bestow sufficient thought upon them, for these 
are suns, though they may be small ones ; and what a 
birth is that for a sun! 

Look now again at the glowing spirals. We ob- 
serve that hardly have they left the central mass be- 
fore they begin to coagulate. In some places they 
have a **ropy" aspect; or they are like peascods filled 
6 95 



CURIOSITIES OF THE SKY 

with growing seeds, which eventually will become 
stars. The great focus itself shows a similar tendency, 
especially around its circumference. The sense that 
it imparts of a tremendous shattering force at work 
is overwhelming. There is probably more matter in 
that whirling and bursting nebula than would suffice 
to make a hundred solar systems ! It must be con- 
fessed at once that there is no confirmation of the 
Laplacean hypothesis here; but what hypothesis will 
fit the facts ? There is one which it has been claimed 
does so, but we shall come to that later. In the 
meanwhile, as a preparation, fix in the memory the 
appearance of that second spiral mass spinning be- 
side its master which seems to have spurned it 
away. 

For a second example of the spiral nebulae look at 
the one in the constellation Triangulum. God, how 
hath the imagination of puny inan failed to comprehend 
Thee! Here is creation through destruction with a 
vengeance! The spiral form of the nebula is un- 
mistakable, but it is half obliterated amid the turmoil 
of flying masses hurled away on all sides with tornadic 
fury. The focus itself is splitting asunder under the 
intolerable strain, and in a little while, as time is 
reckoned in the Cosmos, it will be gyrating into stars. 
And then look at the cyclonic rain of already finished 
stars whirling round the outskirts of the storm. 
Observe how scores of them are yet involved in the 
fading streams of the nebulous spirals ; see how they 
have been thrown into vast loops and curves, of a 
beauty that half redeems the terror of the spectacle 
enclosed within their lines — like iridescent cirri hover- 

96 




SPIRAL IN URSA MAJOR 



WHIRLING NEBULA 

ing about the edges of a hurricane. And so again 
are suns born! 

Let us turn to the exquisite spiral in Ursa Major; 
how different its aspect from that of the other! One 
would say that if the terrific coil in Triangulum has 
all but destroyed itself in its fury, this one on the con- 
trary has just begun its self-demolition. As one 
gazes one seems to see in it the smooth, swift, accelerat- 
ing motion that precedes catastrophe. The central 
part is still intact, dense, and uniform in texture. 
How graceful are the spirals that smoothly rise from 
its oval rim and, gemmed with little stars, wind off 
into the darkness until they have become as delicate 
as threads of gossamer! But at bottom the story told 
here is the same — creation by gyration! 

Compare with the above the curious mass in Cetus. 
Here the plane of the whirling nebula nearly coincides 
with our line of sight and we see the object at a low 
angle. It is far advanced and torn to shreds, and if 
we could look at it perpendicularly to its plane it is 
evident that it would closely resemble the spectacle 
in Triangulum. 

Then take the famous Andromeda Nebula (see 
Frontispiece), which is so vast that notwithstanding 
its immense distance even the naked eye perceives it 
as an enigmatical wisp in the sky. Its image on the 
sensitive plate is the masterpiece of astronomical pho- 
tography; for wild, incomprehensible beauty there is 
nothing that can be compared with it. Here, if any- 
where, we look upon the spectacle of creation in one of 
its earliest stages. The Andromeda Nebula is appar- 
ently less advanced toward transformation into stellar 

99 



CURIOSITIES OF THE SKY 

bodies than is that in Triangulum. The immense 
crowd of stars sprinkled over it and its neighborhood 
seem in the main to lie this side of the nebula, and con- 
sequently to have no connection with it. But incip- 
ient stars (in some places clusters of them) are seen 
in the nebulous rings, while one or two huge masses 
seem to give promise of transformation into stellar 
bodies of unusual magnitude. I say "rings" because 
although the loops encompassing the Andromeda Neb- 
ebula have been called spirals by those who wish ut- 
terly to demolish Laplace's hypothesis, yet they are not 
manifestly such, as can be seen on comparing them 
with the undoubted spirals of the Lord Rosse Nebula. 
They look quite as much like circles or ellipses seen at 
an angle of, say, fifteen or twenty degrees to their 
plane. If they are truly elliptical they accord fairly 
well with Laplace's idea, except that the scale of 
magnitude is stupendous, and if the Andromeda 
Nebula is to become a solar system it will surpass ours 
in grandeur beyond all possibility of comparison. 

There is one circumstance connected with the spiral 
nebulas, and conspicuous in the Andromeda Nebula 
on account of its brightness, which makes the ques- 
tion of their origin still more puzzling; they all show 
continuous spectra, which, as we have before remarked, 
indicate that the mass from which the light comes is 
either solid or liquid, or a gas under heavy pressure. 
Thus nebulas fall into two classes: the ''white" 
nebulas, giving a continuous spectrum; and the 
"green" nebulae whose spectra are distinctly gaseous. 
The Andromeda Nebula is the great representative 
of the former class and the Orion Nebula of the latter. 

JQQ 




NEBULA IN CETUS 



WHIRLING NEBULA 

The spectrum of the Andromeda Nebula has been 
interpreted to mean that it consists not of luminous 
gas, but of a flock of stars so distant that they are 
separately indistinguishable even with powerful tele- 
scopes, just as the component stars of the Milky Way 
are indistinguishable with the naked eye; and upon 
this has been based the suggestion that what we see 
in Andromeda is an outer universe whose stars form 
a series of elliptical garlands surrounding a central 
mass of amazing richness. But this idea is unac- 
ceptable if for no other reason than that, as just said, 
all the spiral nebula possess the same kind of spec- 
trum, and probably no one would be disposed to re- 
gard them all as outer universes. As we shall see later, 
the peculiarity of the spectra of the spiral nebula is 
appealed to in support of a modern substitute for 
Laplace's hypothesis. 

Finally, without having by any means exhausted 
the variety exhibited by the spiral nebula, let us 
turn to the great representative of the other species, 
the Orion Nebula. In some ways this is even more 
marvellous than the others. The early drawings with 
the telescope failed to convey an adequate con- 
ception either of its sublimity or of its complication 
of structure. It exists in a nebulous region of space, 
since photographs show that nearly the whole con- 
stellation is interwoven with faintly luminous coils. 
To behold the entry of the great nebula into the field 
even of a small telescope is a startling experience which 
never loses its novelty. As shown by the photo- 
graphs, it is an inscrutable chaos of perfectly amazing 
extent, where spiral bands, radiating streaks, dense 

103 



CURIOSITIES OF THE SKY 

masses, and dark yawning gaps are strangely inter- 
mingled without apparent order. In one place four 
conspicuous little stars, better seen with a telescope 
than in the photograph on account of the blurring 
produced by over-exposure, are suggestively situated 
in the midst of a dark opening, and no observer has 
ever felt any doubt that these stars have been formed 
from the substance of the surrounding nebula. There 
are many other stars scattered over its expanse which 
manifestly owe their origin to the same source. But 
compare the general appearance of this nebula with 
the others that we have studied, and remark the dif- 
ference. If the unmistakably spiral nebulae resemble 
bursting fly-wheels or grindstones from whose perim- 
eters torrents of sparks are flying, the Orion Nebula 
rather recalls the aspect of a cloud of smoke and 
fragments produced by the explosion of a shell. This 
idea is enforced by the look of the outer portion far- 
thest from the bright half of the nebula, where sharply 
edged clouds with dark spaces behind seem to be 
billowing away as if driven by a wind blowing from 
the centre. 

Next let us consider what scientific speculation has 
done in the effort to explain these mysteries. La- 
place's hypothesis can certainly find no standing 
ground either in the Orion Nebula or in those of a 
spiral configuration, whatever may be its situation 
with respect to the grand Nebula of Andromeda, or 
the ''ring" and ''planetary" nebulas. Some other 
hypothesis more consonant with the appearances 
must be found. Among the many that have been 
proposed the most elaborate is the " Planetesimal 

104 



, ■ -JjI 


'^^HJ^^^HKi:- ' 


* 


• ' • 




• 


• .:.. 'P^.' ■-* 




m 








• 

• • 




^^ 




^HH^^^^HP^- 


it^. • 




• 


• 



THE ORION NEBULA 



WHIRLING NEBULA 

Hypothesis" of Professors Chamberlin and Moulton. 
It is to be remarked that it appHes to the spiral 
nebulae distinctively, and not to an apparently chaotic 
mass of gas like the vast luminous cloud in Orion. 
The gist of the theory is that these curious objects 
are probably the result of close approaches to each 
other of two independent suns, reminding us of what 
was said on this subject when we were dealing with 
temporary stars. Of the previous history of these 
appulsing suns the theory gives us no account ; they are 
simply supposed to arrive within what may be called 
an effective tide-producing distance, and then the 
drama begins. Some of the probable consequences 
of such an approach have been noticed in Chapter V ; 
let us now consider them a little more in detail. 

Tides always go in couples ; if there is a tide on one 
side of a globe there will be a corresponding tide on 
the other side. The cause is to be found in the law 
that the force of gravitation varies inversely as the 
square of the distance; the attraction on the nearest 
surface of a body exercised by another body is 
greater than on its centre, and greater yet than on its 
opposite surface. If two great globes attract each 
other, each tends to draw the other out into an 
ellipsoidal figure; they must be more rigid than steel 
to resist this — and even then they cannot altogether 
resist. If they are liquid or gaseous they will yield 
readily to the fores of distortion, the amount of which 
will depend upon their distance apart, for the nearer 
they are the greater becomes the tidal strain. If 
they are encrusted without and liquid or gaseous in 
the interior, the internal mass will strive to assume 

107 



CURIOSITIES OF THE SKY 

the figure demanded by the tidal force, and will, if it 
can, burst the restraining envelope. Now this is 
virtually the predicament of the body we call a sun 
when in the immediate presence of another body of 
similarly great mass. Such a body is presumably 
gaseous throughout, the component gases being held 
in a state of rigidity by the compression produced by 
the tremendous gravitational force of their own 
aggregate mass. At the surface such a body is en- 
veloped in a shell of relatively cool matter. Now 
suppose a great attracting body, such as another sun, 
to approach near enough for the difference in its 
attraction on the two opposite sides of the body 
and on its centre to become very great; the conse- 
quence will be a tidal deformation of the whole body, 
and it will lengthen out along the line of the gravita- 
tional pull and draw in at the sides, and if its shell 
offers considerable resistance, but not enough to 
exercise a complete restraint, it will be violently burst 
apart, or blown to atoms, and the internal mass will 
leap out on the two opposite sides in great fiery 
spouts. In the case of a sun further advanced in 
cooling than ours the interior might be composed of 
molten matter while the exterior crust had become 
rigid like the shell of an egg; then the force of the 
"tidal explosion" produced by the appulse of another 
sun would be more violent in consequence of the 
greater resistance overcome. Such, then, is the 
mechanism of the first phase in the history of a spiral 
nebula according to the Planetesimal Hypothesis. 
Two suns, perhaps extinguished ones, have drawn near 
together, and an explosive outburst has occurred in 

io8 



WHIRLING NEBULA 

one or both. The second phase calls for a more agile 
exercise of the imagination. 

To simplify the case, let us suppose that only one 
of the tugging suns is seriously affected by the strain. 
Its vast wings produced by the outburst are twisted 
into spirals by their rotation and the contending 
attractions exercised upon them, as the two suns, like 
battleships in desperate conflict, curve round each 
other, concentrating their destructive energies. Then 
immense quantities of debris are scattered about in 
which eddies are created, and finally, as the sun that 
caused the damage goes on its way, leaving its victim 
to repair its injuries as it may, the dispersed matter 
cools, condenses, and turns into streams of solid 
particles circling in elliptical paths about their parent 
sun. These particles, or fragments, are the ''plane- 
tesimals" of the theory. In consequence of the in- 
evitable intersection of the orbits of the planet esimals, 
nodes are formed where the flying particles meet, and 
at these nodes large masses are gradually accumulated. 
The larger the mass the greater its attraction, and at 
last the nodal points become the nuclei of great 
^-ggregations from which planets are shaped. 

This, in very brief form, is the Planetesimal Hypoth- 
esis which we are asked to substitute for that based 
on Laplace's suggestion as an explanation of the mode 
of origin of the solar system; and the phenomena of 
the spiral nebulae are appealed to as offering evident 
support to the new hypothesis. We are reminded 
that they are elliptical in outline, which accords with 
the hypothesis; that their spectra are not gaseous, 
which shows that they may be composed of solid 

109 



CURIOSITIES OF THE SKY 

particles like the planetesimals ; and that their central 
masses present an oval form, which is what would 
result from the tidal effects, as just described. We 
also remember that some of them, like the Lord Rosse 
and the Andromeda nebulae, are visually double, and 
in these cases we might suppose that the two masses 
represent the tide-burst suns that ventured into too 
close proximity. It may be added that the authors 
of the theory do not insist upon the appulse of two 
suns as the only way in which the planetesimals may 
have originated, but it is the only supposition that 
has been worked out. 

But serious questions remain. It needs, for instance, 
but a glance at the Triangulum monster to convince 
the observer that it cannot be a solar system which 
is being evolved there, but rather a swarm of stars. 
Many of the detached masses are too vast to admit 
of the supposition that they are to be transformed 
into planets, in our sense of planets, and the distances 
of the stars which appear to have been originally 
ejected from the focal masses are too great to allow 
us to liken the assemblage that they form to a solar 
system. Then, too, no nodes such as the hypothesis 
calls for are visible. Moreover, in most of the spiral 
nebulae the appearances favor the view that the 
supposititious encountering suns have not separated 
and gone each rejoicing on its way, after having in- 
flicted the maximum possible damage on its opponent, 
but that, on the contrary, they remain in close associa- 
tion like two wrestlers who cannot escape £rom each 
other's grasp. And this is exactly what the law of 
gravitation demands; stars cannot approach one 

IIO 



WHIRLING NEBULA 

another with impunity, with regard either to their 
physical make-up or their future independence of 
movement. The theory undertakes to avoid this 
difficulty by assuming that in the case of our system 
the approach of the foreign body to the sun was not a 
close one — just close enough to produce the tidal e^:- 
trusion of the relatively insignificant quantity of 
matter needed to form the planets. But even then 
the effect of the appulse would be to change the 
direction of flight, both of the sun and of its visitor, 
and there is no known star in the sky which can be 
selected as the sun's probable partner in their ancient 
pas deux. That there are unconquered difficulties 
in Laplace's hypothesis no one would deny, but in 
simplicity of conception it is incomparably more 
satisfactory, and with proper modifications could 
probably be made more consonant with existing facts 
in our solar system than that which is offered to re- 
place it. Even as an explanation of the spiral nebulas, 
not as solar systems in process of formation, but as the 
birthplaces of stellar clusters, the Planetesimal 
Hypothesis would be open to many objections. Grant- 
ing its assumptions, it has undoubtedly a strong math- 
ematical framework, but the trouble is not with the 
mathematics but with the assumptions. Laplace 
was one of the ablest mathematicians that ever 
lived, but he had never seen a spiral nebula; if he 
had, he might have invented a hypothesis to suit its 
phenomena. His actual hypothesis was intended 
only for our solar system, and he left it in the form of 
a ''note" for the consideration of his successors, with 
the hope that they might be able to discover the full 

III 



CURIOSITIES OF THE SKY 

truth, which he confessed was hidden from him. It 
cannot be said that that truth has yet been found, 
and when it is found the chances are that intuition 
and not logic will have led to it. 

The spiral nebula, then, remain among the greatest 
riddles of the universe, while the gaseous nebula, 
like that of Orion, are no less mysterious, although it 
seems impossible to doubt that both forms give birth 
to stars. It is but natural to look to them for light 
on the question of the origin of our planetary system ; 
but we should not forget that the scale of the phe- 
nomena in the two cases is vastly different, and the 
forces in operation may be equally different. A hill 
may have been built up by a glacier, while a mountain 
may be the product of volcanic forces or of the up- 
heaval of the strata of the planet. 



VII 

THE BANNERS OP THE SUN 

AS all the world knows the sun, it is a blinding 
i\ globe, pouring forth an inconceivable quantity 
of light and heat, whose daily passage through the 
sky, caused by the earth's rotation on its axis, con- 
stitutes the most important phenomenon of terrestrial 
existence. Viewed with a dark glass to take off the 
glare, or with a telescope, its rim is seen to be a sharp 
and smooth circle, and nothing but dark sky is visible 
around it. Except for the interference of the moon, 
we should probably never have known that there is 
any more of the sun than our eyes ordinarily see. 

But when an eclipse of the sun occurs, caused by 
the interposition of the opaque globe of the moon, 
we see its immediate surroundings, which in some 
respects are more wonderful than the glowing central 
orb. These surroundings, although not in the sense 
in which we apply the term to the gaseous envelope 
of the earth, may be called the sun's atmosphere. 
They consist of two very different parts — first, the 
red ''prominences," which resemble tongues of flame 
ascending thousands of miles above the sun's surface ; 
and, second, the ''corona," which extends to distances 
of millions of miles from the sun, and shines with a 

113 



CURIOSITIES OF THE SKY 

soft, glowing light . The two combined, when well seen, 
make a spectacle without parallel among the marvels 
of the sky. Although many attempts have been made 
to render the corona visible when there is no eclipse, 
all have failed, and it is to the moon alone that we owe 
its revelation. To cover the sun's disk with a cir- 
cular screen will not answer the purpose because of 
the illumination of the air all about the observer. 
When the moon hides the sun, on the other hand, 
the sunlight is withdrawn from a great cylinder of air 
extending to the top of the atmosphere and spreading 
many miles around the observer. There is then no 
glare to interfere with the spectacle, and the corona 
appears in all its surprising beauty. The prominences, 
however, although they were discovered during an 
eclipse, can now, with the aid of the spectroscope, be 
seen at any time. But the prominences are rarely 
large enough to be noticed by the naked eye, while 
the streamers of the corona, stretching far away in 
space, like ghostly banners blown out from the black 
circle of the obscuring moon, attract every eye, and 
to this weird apparition much of the fear inspired 
by eclipses has been due. But if the corona has been 
a cause of terror in the past it has become a source of 
growing knowledge in our time. 

The story of the first scientific observation of the 
corona and the prominences is thrillingly interesting, 
and in fact dramatic. The observation was made 
during the eclipse of 1842, which fortunately was 
visible all over Central and Southern Europe so that 
scores of astronomers saw it. The interest centres 
in what happened at Pavia in Northern Italy, where 

114 




THE CORONA 



THE BANNERS OF THE SUN 

the English astronomer Francis Baily had set up his 
telescope. The eclipse had begun and Baily was busy 
at his telescope when, to quote his own words in the 
account which he wrote for the Memoirs of the Royal 
Astronomical Society: ''I was astounded by a tre- 
mendous burst of applause from the streets below, 
and at the same moment was electrified by the sight 
of one of the most brilliant and splendid phenomena 
that can well be imagined ; for at that instant the 
dark body of the moon was suddenly surrounded with 
a corona, or kind of bright glory, similar in shape and 
magnitude to that which painters draw round the 
heads of saints. . . . Pavia contains many thousand 
inhabitants, the major part of whom were at this 
early hour walking about the streets and squares or 
looking out of windows in order to witness this long- 
talked-of phenomenon; and when the total obscura- 
tion took place, which was instantaneous, there was a 
universal shout from every observer which *made 
the welkin ring,' and for the moment withdrew my 
attention from the object with which I was imme- 
diately occupied. I had, indeed, expected the ap- 
pearance of a luminous circle round the moon during 
the time of total obscurity; but I did not expect, 
from any of the accounts of preceding eclipses that I 
had read, to witness so magnificent an exhibition as 
that which took place. . . . Splendid and astonishing, 
however, as this remarkable phenomenon really was, 
and although it could not fail to call forth the admira- 
tion and applause of every beholder, yet I must con- 
fess that there was at the same time something in its 
singular and wonderful appearance that was appalling. 

117 



CURIOSITIES OF THE SKY 

. . . But the most remarkable circumstance attending 
the phenomenon was the appearance of three large 
protuberances apparently emanating from the circum- 
ference of the moon, but evidently forming a portion 
of the corona. They had the appearance of moun- 
tains of a prodigious elevation; their color was red 
tinged with lilac or purple ; perhaps the color of the 
peach-blossom would more nearly represent it. They 
somewhat resembled the tops of the snowy Alpine 
mountains when colored by the rising or the setting 
sun. They resembled the Alpine mountains also in 
another respect, inasmuch as their light was perfectly 
steady, and had none of that flickering or sparkling 
motion so visible in other parts of the corona. . . . 
The whole of these protuberances were visible even 
to the last moment of total obscuration, and when 
the first ray of light was admitted from the sun they 
vanished, with the corona, altogether, and daylight 
was instantly restored." 

I have quoted nearly all of this remarkable descrip- 
tion not alone for its intrinsic interest, but because 
it is the best depiction that can be found of the general 
phenomena of a total solar eclipse. Still, not every 
such eclipse offers an equally magnificent spectacle. 
The eclipses of 1900 and 1905, for instance, which 
were seen by the writer, the first in South Carolina and 
the second in Spain, fell far short of that described 
by Baily in splendor and impressiveness. Of course, 
something must be allowed for the effect of surprise; 
Baily had not expected to see what was so suddenly 
disclosed to him. But both in 1900 and 1905 the 
amount of scattered light in the sky was sufficient in 

118 



THE BANNERS OF THE SUN 

itself to make the corona appear faint, and there were 
no very conspicuous prominences visible. Yet on 
both occasions there was manifest among the specta- 
tors that mingling of admiration and awe of which 
Baily speaks. The South Carolinians gave a cheer 
and the ladies waved their handkerchiefs when the 
corona, ineffably delicate of form and texture, melted 
into sight and then in two minutes melted away 
again. The Spaniards, crowded on the citadel hill 
of Burgos, with their king and his royal retinue in 
their midst, broke out with a great clapping of hands 
as the awaited spectacle unfolded itself in the sky; 
and on both occasions, before the applause began, 
after an awed silence a low murmur ran through the 
crowds. At Burgos it is said many made the sign of 
the cross. 

It was not long before Baily's idea that the promi- 
nences were a part of the corona was abandoned, and 
it was perceived that the two phenomena were to a 
great extent independent. At the eclipse of 1868, 
which the astronomers, aroused by the wonderful 
scene of 1842, and eager to test the powers of the 
newly invented spectroscope, flocked to India to 
witness, Janssen conceived the idea of employing the 
spectroscope to render the prominences visible when 
there was no eclipse. He succeeded the very next 
day, and these phenomena have been studied in that 
way ever since. 

There are recognized two kinds of prominences — 
the ** eruptive" and the ''quiescent." The latter, 
which are cloud-like in form, may be seen almost any- 
where along the edge of the sun; but the former, 
7 119 



CURIOSITIES OF THE SKY 

which often shoot up as if hurled from mighty vol- 
canoes, appear to be associated with sun-spots, and 
appear only above the zones where spots abound. 
Either of them, when seen in projection against the 
brilliant solar disk, appears white, not red, as against 
a background of sky. The quiescent prominences, 
whose elevation is often from forty thousand to sixty 
thousand miles, consist, as the spectroscope shows, 
mainly of hydrogen and helium. The latter, it will be 
remembered, is an element which was known to be in 
the sun many years before the discovery that it also 
exists in small quantities on the earth. A fact which 
may have a significance which we cannot at present 
see is that the emanation from radium gradually and 
spontaneously changes into helium, an alchemistical 
feat of nature that has opened many curious vistas 
to speculative thinkers. The eruptive prominences, 
which do not spread horizontally like the others, but 
ascend with marvellous velocity to elevations of half 
a million rniles or more, are apparently composed 
largely of metallic vapors — i.e.^ metals which are 
usually solid on the earth, but which at solar tem- 
peratures are kept in a volatilized state. The 
velocity of their ascent occasionally amounts to 
three hundred or four hundred miles per second. It 
is known from mathematical considerations that the 
gravitation of the sun would not be able to bring back 
any body that started from its surface with a velocity 
exceeding three hundred and eighty-three miles per 
second ; so it is evident that some of the matter hurled 
forth in eruptive prominences may escape from 
solar control and go speeding out into space, cooling 

120 




A SOLAR PROMINENCE. PHOTOGRAPHED MAY 21, I907 



THE BANNERS OF THE SUN 

and condensing into solid masses. There seems to be 
no reason why some of the projectiles from the sun 
might not reach the planets. Here, then, we have, 
on a relatively small scale, explosions recalling those 
which it has been imagined may be the originating 
cause of some of the sudden phenomena of the stellar 
heavens. 

Of the sun-spots it is not our intention here specially 
to speak, but they evidently have an intimate con- 
nection with eruptive prominences, as well as some 
relation, not yet fully understood, with the corona. 
Of the real cause of sun-spots we know virtually noth- 
ing, but recent studies by Professor Hale and others 
have revealed a strange state of things in the clouds of 
metallic vapors floating above them and their sur- 
roundings. Evidences of a cyclonic tendency have 
been found, and Professor Hale has proved that sun- 
spots are strong magnetic fields, and consist of 
columns of ionized vapors rotating in opposite 
directions in the two hemispheres. A fact which may 
have the greatest significance is that titanium and 
vanadium have been found both in sun-spots and 
in the remarkable variable Mira Ceti, a star which 
every eleven months, or thereabout, flames up with 
great brilliancy and then sinks back to invisibility 
with the naked eye. It has been suggested that sun- 
spots are indications of the beginning of a process in 
the sun which will be intensified until it falls into the 
state of such a star as Mira. Stars very far advanced 
in evolution, without showing variability, also ex- 
hibit similar spectra ; so that there is much reason for 
regarding sunspots as emblems of advancing age. 

123 



CURIOSITIES OF THE SKY 

The association of the corona with sun-spots is less 
evident than that of the eruptive prominences; still 
such an association exists, for the form and extent of 
the corona vary with the sun-spot period of which we 
shall presently speak. The constitution of the corona 
remains to be discovered. It is evidently in part 
gaseous, but it also probably contains matter in the 
form of dust and small meteors. It includes one 
substance altogether mysterious — ' ' coronium . ' ' There 
are reasons for thinking that this may be the lightest 
of all the elements, and Professor Young, its dis- 
coverer, said that it was "absolutely unique in nature ; 
utterly distinct from any other known form of matter, 
terrestrial, solar, or cosmical." The enormous ex- 
tent of the corona is one of its riddles. Since the 
development of the curious subject of the ''pressure of 
light" it has been proposed to account for the sus- 
tentation of the gorona by supposing that it is borne 
upon the billows of light continually poured out from 
the sun. Experiment has proved, what mathemat- 
ical considerations had previously pointed out as 
probable, that the waves of light exert a pressure or 
driving force, which becomes evident in its effects if 
the body acted upon is sufficiently small. In that 
case the light pressure will prevail over the attraction 
of gravitation, and propel the attenuated matter 
away from the sun in the teeth of its attraction. The 
earth itself would be driven away if, instead of con- 
sisting of a solid globe of immense aggregate mass, 
it were a cloud of microscopic particles. The reason 
is that the pressure varies in proportion to the sur- 
face of the body acted upon, while the gravitational 

124 



THE BANNERS OP THE SUN 

attraction is proportional to the volume, or the total 
amount of matter in the body. But the surface of 
any body depends upon the square of its diameter, 
while the volume depends upon the cube of the 
diameter. If, for instance, the diameter is represented 
by 4, the surface will be proportional to 4 x 4, or 16, 
and the volume to 4 x 4 x 4, or 64; but if the diameter 
is taken as 2, the surface will be 2 x 2, or 4, and the 
volume 2 X 2 x 2, or 8. Now, the ratio of 4 to 8 is 
twice as great as that of 16 to 64. If the diameter 
is still further decreased, the ratio of the surface to the 
volume will proportionally grow larger; in other words, 
the pressure will gain upon the attraction, and what- 
ever their original ratio may have been, a time will 
come, if the diminution of size continues, when the 
pressure will become more effective than the attraction, 
and the body will be driven away. Supposing the par- 
ticles of the corona to be below the critical size for the 
attraction of a mass like that of the sun to control 
them, they would be driven off into the surrounding 
space and appear around the sun like the clouds of dust 
around a mill. We shall return to this subject in 
connection with the Zodiacal Light, the Aurora, and 
Comets. 

On the other hand, there are parts of the corona 
which suggest by their forms the play of electric or 
magnetic forces. This is beautifully shown in some 
of the photographs that have been made of the corona 
during recent eclipses. Take, for instance, that of the 
eclipse of 1900. The sheaves of light emanating from 
the poles look precisely like the "lines of force" sur- 
rounding the poles of a magnet. It will be noticed 

125 



CURIOSITIES OP THE SKY 

in this photograph that the corona appears to consist 
of two portions: one comprising the polar rays just 
spoken of, and the other consisting of the broader, 
longer, and less-defined masses of light extending out 
from the equatorial and middle-latitude zones. Yet 
even in this more diffuse part of the phenomenon one 
can detect the presence of submerged curves bearing 
more or less resemblance to those about the poles. 
Just what part electricity or electro-magnetism plays 
in the mechanism of the solar radiation it is im- 
possible to say, but on the assumption that it is a very 
important part is based the hypothesis that there 
exists a direct solar influence not only upon the mag- 
netism, but upon the weather of the earth. This hy- 
pothesis has been under discussion for half a century, 
and still we do not know just how much truth it rep- 
resents. It is certain that the outbreak of great dis- 
turbances on the sun, accompanied by the formation of 
sun-spots and the upshooting of eruptive prominences 
(phenomena which we should naturally expect to be 
attended by action), have been instantly followed by 
corresponding ''magnetic storms" on the earth and 
briUiant displays of the auroral lights. There have 
been occasions when the influence has manifested 
itself in the most startling ways, a great solar outburst 
being followed by a mysterious gripping of the cable 
and telegraph systems of the world, as if an invisible 
and irresistible hand had seized them. Messages are 
abruptly cut off, sparks leap from the telegraph in- 
struments, and the entire earth seems to have been 
thrown into a magnetic flurry. These occurrences 
affect the mind with a deep impression of the depend- 

126 



THE BANNERS OF THE SUN 

ence of our planet on the sun, such as we do not derive 
from the more familiar action of the sunlight on the 
growth of plants and other phenomena of life de- 
pending on solar influences. 

Perhaps the theory of solar magnetic influence upon 
the weather is best known in connection with the 
*' sun-spot cycle." This, at any rate, is, as already 
remarked, closely associated with the corona. Its 
existence was discovered in 1843 t>y the German as- 
tronomer Schwabe. It is a period of variable length, 
averaging about eleven years, during which the num- 
ber of spots visible on the sun first increases to a 
maximum, then diminishes to a minimum, and finally 
increases again to a maximum. For unknown reasons 
the period is sometimes two or three years longer than 
the average and sometimes as much shorter. Never- 
theless, the phenomena always recur in the same order. 
Starting, for instance, with a time when the observer 
can find few or no spots, they gradually increase in 
number and size until a maximum, in both senses, is 
reached, during which the spots are often of enormous 
size and exceedingly active. After two or three years 
they begin to diminish in number, magnitude, and 
activity until they almost or quite disappear. A 
strange fact is that when a new period opens, the spots 
appear first in high northern and southern latitudes, 
far from the solar equator, and as the period ad- 
vances they not only increase in number and size, but 
break out nearer and nearer to the equator, the last 
spots of a vanishing period sometimes lingering in the 
equatorial region after the advance-guard of its suc- 
cessor has made its appearance in the high latitudes. 

127 



CURIOSITIES OF THE SKY 

Spots are never seen on the equator nor near the 
poles. It was not very long after the discovery of 
the sun-spot cycle that the curious observation was 
made that a striking coincidence existed between the 
period of the sun-spots and another period affecting 
the general magnetic condition of the earth. When a 
curved line representing the varying number of sun- 
spots was compared with another curve showing the 
variations in the magnetic state of the earth the two 
were seen to be in almost exact accord, a rise in one 
curve corresponding to a rise in the other, and a fall 
to a fall. Continued observation has proved that this 
is a real coincidence and not an accidental one, so 
that the connection, although as yet unexplained, is 
accepted as established. But does the influence ex- 
tend further, and directly affect the weather and the 
seasons as well as the magnetic elements on the earth ? 
A final answer to this question cannot yet be given, 
for the evidence is contradictory, and the interpreta- 
tions put upon it depend largely on the predilections 
of the judges. 

But, in a broad sense, the sun-spots and the phenom- 
ena connected with them must have a relation to 
terrestrial meteorology, for they prove the sun to be a 
variable star. Reference was made, a few lines above, 
to the resemblance of the spectra of sun-spots to 
those of certain stars which seem to be failing through 
age. This in itself is extremely suggestive ; but if this 
resemblance had never been discovered, we should 
have been justified in regarding the sun as variable 
in its output of energy; and not only variable, but 
probably increasingly so. The very inequalities in 

128 



THE BANNERS OF THE SUN 

the sun-spot cycle are suspicious. When the sun is 
most spotted its total light may be reduced by one- 
thousandth part, although it is by no means certain 
that its outgiving of thermal radiations is then re- 
duced. A loss of one-thousandth of its luminosity 
would correspond to a decrease of .0025 of a stellar 
magnitude, considering the sun as a star viewed from 
distant space. So slight a change would not be per- 
ceptible ; but it is not alone sun-spots which obscure 
the solar surface, its entire globe is enveloped with an 
obscuring veil. When studied with a powerful tele- 
scope the sun's surface is seen to be thickly mottled 
with relatively obscure specks, so numerous that it 
has been estimated that they cut off from one-tenth 
to one-twentieth of the light that we should receive 
from it if the whole surface were as brilliant as its 
brightest parts. The condition of other stars warrants 
the conclusion that this obscuring envelope is the prod- 
uct of a process of refrigeration which will gradually 
make the sun more and more variable until its history 
ends in extinction. Looking backward, we see a time 
when the sun must have been more brilliant than it is 
now. At that time it probably shone with the blind- 
ing white splendor of such stars as Sirius, Spica, and 
Vega; now it resembles the relatively dull Procyon; 
in time it will turn ruddy and fall into the closing 
cycle represented by Antares. Considering that once 
it must have been more radiantly powerful than at 
present, one is tempted to wonder if that could have 
been the time when tropical life flourished within the 
earth's polar circles, sustained by a vivific energy 
in the sun which it has now lost. 

129 



CURIOSITIES OF THE SKY 

The corona, as we have said, varies with the sun- 
spot cycle. When the spots are abundant and active the 
corona rises strong above the spotted zones, forming 
immense beams or streamers, which on one occasion, 
at least, had an observed length of ten million miles. 
At the time of a spot minimum the corona is less brill- 
iant and has a different outline. It is then that the 
curved polar rays are most conspicuous. Thus the 
vast banners of the sun, shaken out in the eclipse, are 
signals to tell of its varying state, but it will probably 
be long before we can read correctly their messages. 



VIII 

THE ZODIACAL LIGHT MYSTERY 

THERE is a singular phenomenon in the sky — one 
of the most puzzHng of all — which has long 
arrested the attention of astronomers, defying their 
efforts at explanation, but which probably not one 
in a hundred, and possibly not one in a thousand, of 
the readers of this book has ever seen. Yet its 
name is often spoken, and it is a conspicuous object 
if one knows when and where to look for it, and 
when well seen it exhibits a mystical beauty which 
at the same time charms and awes the beholder. It 
is called "The Zodiacal Light," because it lies within 
the broad circle of the Zodiac, marking the sun's 
apparent annual path through the stars. What it is 
nobody has yet been able to find out with certainty, 
and books on astronomy usually speak of it with 
singular reserve. But it has given rise to many 
remarkable theories, and a true explanation of it 
would probably throw light on a great many other 
celestial mysteries. The Milky Way is a more won- 
derful object to look upon, but its nature can be com- 
prehended, while there is a sort of uncanniness about 
the Zodiacal Light which immediately impresses one 
upon seeing it, for its part in the great scheme of 
extra-terrestrial affairs is not evident. 

131 



CURIOSITIES OF THE SKY 

If you are out-of-doors soon after sunset — say, on an 
evening late in the month of February — ^you may per- 
ceive, just after the angry flush of the dying winter's 
day has faded from the sky, a pale ghostly presence 
rising above the place where the sun went down. 
The writer remembers from boyhood the first time it 
was pointed out to him and the unearthly impression 
that it made, so that he afterward avoided being out 
alone at night, fearful of seeing the spectral thing 
again. The phenomenon brightens slowly with the 
fading of the twilight, and soon distinctly assumes 
the shape of an elongated pyramid of pearly light, 
leaning toward the south if the place of observation 
is in the northern hemisphere. It does not impress the 
observer at all in the same manner as the Milky Way ; 
that looks far off and is clearly among the stars, but 
the Zodiacal Light seems closer at hand, as if it were 
something more intimately concerning the earth. To 
all it immediately suggests a connection, also, with 
the sunken sun. If the night is clear and the moon 
absent (and if you are in the country, for city lights 
ruin the spectacles of the sky), you will be able to 
watch the apparition for a long time. You will 
observe that the Light is brightest near the horizon, 
gradually fading as the pyramidal beam mounts 
higher, but in favorable circumstances it may be 
traced nearly to the meridian south of the zenith, 
where its apex at last vanishes in the starlight. It 
continues visible during the evenings of March and 
part of April, after which, ordinarily, it is seen no 
more, or if seen is relatively faint and unimpressive. 
But when autumn comes it appears again, this time 

132 



THE ZODIACAL LIGHT MYSTERY 

not like a wraith hovering above the westward tomb of 
the day-god, but rather Hke a spirit of the morning 
announcing his reincarnation in the east. 

The reason why the Zodiacal Light is best seen in 
our latitudes at the periods just mentioned is because 
at those times the Zodiac is more nearly perpendicular 
to the horizon, first in the west and then in the east ; 
and, since the phenomenon is confined within the 
borders of the Zodiac, it cannot be favorably placed 
for observation when the zodiacal plane is but slightly 
inclined to the horizon. Its faint light requires the 
contrast of a background of dark sky in order to be 
readily perceptible. But within the tropics, where 
the Zodiac is always at a favorable angle, the mys- 
terious light is more constantly visible. Nearly all 
observant travellers in the equatorial regions have 
taken particular note of this phenomenon, for being 
so much more conspicuous there than in the temperate 
zones it at once catches the eye and holds the atten- 
tion as a novelty. Humboldt mentions it many times 
in his works, for his genius was always attracted by 
things out of the ordinary and difficult of explana- 
tion, and he made many careful observations on its 
shape, its brilliancy, and its variations; for there can 
be no doubt that it does vary, and sometimes to an 
astonishing degree. It is said that it once remained 
practically invisible in Europe for several years in 
succession. During a trip to South Africa in 1909 an 
English astronomer, Mr. E. W. Maunder, found a 
remarkable difference between the appearance of the 
Zodiacal Light on his going and coming voyages. 
In fact, when crossing the equator going south he did 

^33 



CURIOSITIES OF THE SKY 

not see it at all; but on returning he had, on March 
6th, when one degree south of the equator, a memora- 
ble view of it. "It was a bright, clear night, and the 
Zodiacal Light was extraordinarily brilliant — brighter 
than he had ever seen it before. The Milky Way 
was not to be compared with it. The brightest part 
extended to 75° from the sun. There was a faint 
and much narrower extension which they could just 
make out beyond the Pleiades along the ecliptic, but 
the greater part of the Zodiacal Light showed as a 
broad truncated column, and it did not appear nearly 
as conical as he had before seen it." 

When out of the brief twilight of intertropical 
lands, where the sun drops vertically to the horizon 
and night rushes on like a wave of darkness, the 
Zodiacal Light shoots to the very zenith, its color is 
described as a golden tint, entirely different from the 
silvery sheen of the Milky Way. If I may venture 
again to refer to personal experiences and impressions, 
I will recall a view of the Zodiacal Light from the 
summit of the cone of Mt. Etna in the autumn of 
the year 1896 (more briefly described in Astronomy 
with the Naked Eye). There are few lofty mountains 
so favorably placed as Etna for observations of this 
kind. It was once resorted to by Prof. George E. 
Hale, in an attempt to see the solar corona without an 
eclipse. Rising directly from sea-level to an elevation 
of nearly eleven thousand feet, the observer on its 
summit at night finds himself, as it were, lost in the 
midst of the sky. But for the black flanks of the 
great cone on which he stands he might fancy himself 
to be in a balloon. On the occasion to which I refer 

134 



THE ZODIACAL LIGHT MYSTERY 

the world beneath was virtually invisible in the 
moonless night. The blaze of the constellations over- 
head was astonishingly brilliant, yet amid all their 
magnificence my attention was immediately drawn 
to a great tapering light that sprang from the place 
on the horizon where the sun would rise later, and 
that seemed to be blown out over the stars like a long, 
luminous veil. It was the finest view of the Zodiacal 
Light that I had ever enjoyed — thrilling in its strange- 
ness — but I w^as almost disheartened by the indif- 
ference of my guide, to whom it was only a light and 
nothing more. If he had no science, he had less 
poetry — rather a remarkable thing, I thought, for a 
child of his clime. The Light appeared to me to be 
distinctly brighter than the visible part of the Milky 
Way which included the brilliant stretches in Auriga 
and Perseus, and its color, if one may speak of color 
in connection with such an object, seemed richer than 
that of the galactic band ; but I did not think of it as 
yellow, although Humboldt has described it as re- 
sembling a golden curtain drawn over the stars, and 
Du Chaillu in Equatorial Africa found it of a bright 
yellow color. It may vary in color as in con- 
spicuousness. The fascination of that extraordinary 
sight has never faded from my memory. I turned to 
regard it again and again, although I had never seen 
the stellar heavens so brilliant, and it was one of the 
last things I looked for when the morning glow began 
softly to mount in the east, and Sicily and the Medi- 
terranean slowly emerged from the profound shadow 
beneath us. 
The Zodiacal Light seems never to have attracted 

135 



CURIOSITIES OF THE SKY 

from astronomers in general the amount of careful 
attention that it deserves; perhaps because so little 
can really be made of it as far as explanation is con- 
cerned. I have referred to the restraint that scientific 
writers apparently feel in speaking of it. The grounds 
for speculation that it affords may be too scanty to 
lead to long discussions, yet it piques curiosity, and 
as we shall see in a moment has finally led to a most 
interesting theory. Once it was the subject of an 
elaborate series of studies which carried the observer 
all round the world. That was in 1845-46, during 
the United States Exploring Expedition that visited 
the then little known Japan. The chaplain of the 
fleet, the Rev. Mr. Jones, went out prepared to study 
the mysterious light in all its phases. He saw it from 
many latitudes on both sides of the equator, and the 
imagination cannot but follow him with keen interest 
in his world-circling tour, keeping his eyes every 
night fixed upon the phantasm overhead, whose 
position shifted with that of the hidden sun. He 
demonstrated that the glow extends at times com- 
pletely across the celestial dome, although it is rel- 
atively very faint directly behind the earth. On his 
return the government published a large volume of his 
observations, in which he undertook to show that the 
phenomenon was due to the reflection of sunlight from 
a ring of meteoric bodies encircling the earth. But, 
after all, this elaborate investigation settled nothing. 
Prof. E. E. Barnard has more recently devoted 
much attention to the Zodiacal Light, as well as to a 
strange attendant phenomenon called the ''Gegen- 
schein," or Counterglow, because it always appears at 

136 



THE ZODIACAL LIGHT MYSTERY 

that point in the sky which is exactly opposite to the 
sun. The Gegenschein is an extremely elusive 
phenomenon, suitable only for eyes that have been 
specially trained to see it. Professor Newcomb has 
cautiously remarked that ' ' it is said that in that point 
of the heavens directly opposite to the sun there is 
an elliptical patch of light. . . . This phenomenon is so 
difficult to account for that its existence is sometimes 
doubted; yet the testimony in its favor is difficult to 
set aside." It certainly cannot be set aside at all 
since the observations of Barnard. I recall an at- 
tempt to see it under his guidance during a visit to 
Mount Hamilton, when he was occupied there with the 
Lick telescope. Of course, both the Gegenschein and 
the Zodiacal Light are too diffuse to be studied with 
telescopes, which, so to speak, magnify them out of 
existence. They can only be successfully studied 
with the naked eye, since every faintest glimmer that 
they afford must be utilized. This is especially true 
of the Gegenschein. At Mount Hamilton, Mr. Barnard 
pointed out to me its location with reference to cer- 
tain stars, but with all my gazing I could not be sure 
that I saw it. To him, on the contrary, it was obvious ; 
he had studied it for months, and was able to indicate 
its shape, its boundaries, its diameter, and the dec- 
lination of its centre with regard to the ecliptic. 
There is not, of course, the shadow of a doubt of the 
existence of the Gegenschein, and yet I question if one 
person in a million has ever seen or ever will see it. 
The Zodiacal Light, on the other hand, is plain enough, 
provided that the timic and the circumstances of the 
observation are properly chosen. 

8 137 



CURIOSITIES OF THE SKY 

In the attempts to explain the Zodiacal Light, the 
favorite hypothesis has been that it is an appendage 
of the sun — perhaps simply an extension of the corona 
in the plane of the eclip . ' ., which is not very far from 
coinciding with that of the sun's equator. This idea 
is quite a natural one, because of the evident relation 
of the light to the position of the sun. The vast ex- 
tension of the equatorial wings of the corona in 1878 
gave apparent support to this hypothesis ; if the sub- 
stance of the corona could extend ten million miles 
from the sun, why might it not extend even one 
hundred million, gradually fading out beyond the 
orbit of the earth? A variation of this hypothesis 
assumes that the reflection is due to swarms of meteors 
circling about the sun, in the plane of its equator, all 
the way from its immediate neighborhood to a distance 
exceeding that of the earth. But in neither form is 
the hypothesis satisfactory; there is nothing in the 
appearance of the corona to indicate that it extends 
even as far as the planet Mercury, while as to meteors, 
the orbits of the known swarms do not accord with 
the hypothesis, and we have no reason to believe that 
clouds of others exist travelling in the part of space 
where they would have to be in order to answer the 
requirements of the theory. The extension of the 
corona in 1878 did not resemble in its texture the 
Zodiacal Light. 

Now, it has so often happened in the history of 
science that an important discovery in one branch 
has thrown unexpected but most welcome light upon 
some pending problem in some other branch, that a 
strong argument might be based upon that fact alone 

138 



THE ZODIACAL LIGHT MYSTERY 

against the too exclusive devotion of many investi- 
gators to the narrow lines of their own particular 
specialty; and the Zodiacal Light affords a case in 
point, when it is considered in connection with recent 
discoveries in chemistry and physics. From the fact 
that atoms are compound bodies made up of corpuscles 
at least a thousand times smaller than the smallest 
known atom — a fact which astounded most men of 
science when it was announced a few years ago — 
a new hypothesis has been developed concerning the 
nature of the Zodiacal Light (as well as other as- 
tronomical riddles), and this hypothesis comes not 
from an astronomer, but from a chemist and physicist, 
the Swede, Svante Arrhenius. In considering an 
outline of this new hypothesis we need neither accept 
nor reject it; it is a case rather for suspension of 
judgment. 

To begin with, it carries us back to the ** pressure 
of light" mentioned in the preceding chapter. The 
manner in which this pressure is believed generally 
to act was there sufficiently explained, and it only 
remains to see how it is theoretically extended to the 
particles of matter supposed to constitute the Zodiacal 
Light. We know that corpuscles, or "fragments of 
atoms'* negatively electrified, are discharged from 
hot bodies. Streams of these *'ions" pour from 
many flames and from molten metals; and the im- 
pact of the cathode and ultra-violet rays causes them 
to gush even from cold bodies. In the vast labora- 
tory of the sun it is but reasonable to suppose that 
similar processes are taking place. '*As a very hot 
metal emits these corpuscles," says Prof. J. J. Thom- 

139 



CURIOSITIES OF THE SKY 

son, "it does not seem an improbable hypothesis that 
they are emitted by that very hot body, the sun." 
Let it be assumed, then, that the sun does emit them ; 
what happens next? Negatively charged corpuscles, 
it is known, serve as nuclei to which particles of matter 
in the ordinary state are attracted, and it is probable 
that those emitted from the sun immediately pick up 
loads in this manner and so grow in bulk. If they 
grow large enough the gravitation of the sun draws 
them back, and they produce a negative charge in the 
solar atmosphere. But it is probable that many 
of the particles do not attain the critical size which, 
according to the principles before explained, would 
enable the gravitation of the sun to retain them in 
opposition to the pressure of the waves of light, and 
with these particles the light pressure is dominant. 
Clouds of them may be supposed to be continually 
swept away from the sun into surrounding space, 
moving mostly in or near the plane of the solar equa- 
tor, where the greatest activity, as indicated by sun- 
spots and related phenomena, is taking place. As 
they pass outward into space many of them en- 
counter the earth. If the earth, like the moon, had 
no atmosphere the particles would impinge directly on 
its surface, giving it a negative electric charge. But 
the presence of the atmosphere changes all that, for 
the first of the flying particles that encounter it im- 
part to it their negative electricity, and then, since 
like electric charges repel like, the storm of particles 
following will be sheered off from the earth, and will 
stream around it in a maze of hyperbolic paths. 
Those that continue on into space beyond the earth 

140 



THE ZODIACAL LIGHT MYSTERY 

may be expected to continue picking up wandering 
particles of matter until their bulk has become so 
great that the solar attraction prevails again over the 
light pressure acting upon them, and they turn again 
sunward. Passing the earth on their return they 
will increase the amount of dust-clouds careering round 
it; and these will be further increased by the action 
of the ultra-violet rays of the sunlight causing par- 
ticles to shoot radially away from the earth when the 
negative charge of the upper atmosphere has reached 
a certain amount, which particles, although starting 
sunward, will be swept back to the earth with the on- 
coming streams. As the final result of all this ac- 
cumulation of flying and gyrating particles in the 
earth's neighborhood, we are told that the latter must 
be transformed into the semblance of a gigantic solid- 
headed comet provided with streaming tails, the 
longest of them stretching away from the direction 
of the sun, while another shorter one extends toward 
the sun. This shorter tail is due to the particles that 
we have just spoken of as being driven sunward from 
the earth by the action of ultra-violet light. No 
doubt this whole subject is too technical for popular 
statement; but at any rate the general reader can 
understand the picturesque side of the theory, for 
its advocates assure us that if we were on the moon 
we should doubtless be able to see the comet-like tails 
of the earth, and then we could appreciate the part 
that they play in producing the phenomenon of the 
Zodiacal Light. 

That the Light as we see it could be produced by 
the reflection of sunlight from swarms of particles 

141 



CURIOSITIES OF THE SKY 

careering round the earth in the manner supposed by 
Arrhenius' hypothesis, is evident enough; and it will 
be observed that the new theory, after all, is only an- 
other variant of the older one which attributes the 
Zodiacal Light to an extension of the solar corona. 
But it differs from the older theory in affording an 
explanation of the manner in which the extension is 
effected, and it differentiates between the corona 
proper and the streams of negative particles shot 
away from the sun. In its details the hypothesis of 
Arrhenius also affords an explanation of many 
peculiarities of the Zodiacal Light, such as that it is 
confined to the neighborhood of the ecliptic, and that 
it is stronger on the side of the earth which is just 
turning away from a position under the sun than on 
the other side; but it would carry us beyond our 
limits to go into these particulars. The Gegenschein, 
according to this theory, is a part of the same phenom- 
enon as the Zodiacal Light, for by the laws of 
perspective it is evident that the reflection from the 
streams of particles situated at a point directly op- 
posite to the sun would be at a maximum, and this 
is the place which the Gegenschein occupies. Apart 
from its geometrical relations to the position of the 
sun, the variability of the Zodiacal Light appears to 
afErm its solar dependence, and this too would be 
accounted for by Arrhenius' hypothesis better than 
by the old theory of coronal extension. The amount 
of corpuscular discharge from the sun must nat- 
urally be governed by the state of relative activity 
or inactivity of the latter, and this could not but be 
reflected in the varying splendor of the Zodiacal 

142 



THE ZODIACAL LIGHT MYSTERY 

Light. But much more extended study than has 
yet been given to the subject will be required before 
we can feel that we know with reasonable certainty 
what this mysterious phenomenon really is. By the 
hypothesis of Arrhenius every planet that has an 
atmosphere must have a Zodiacal Light attending it, 
but the phenomenon is too faint for us to be able to 
see it in the case, for instance, of Venus, whose at- 
mosphere is very abundant. The moon has no 
corresponding ''comet's tail" because, as already ex- 
plained, of the lack of a lunar atmosphere to repel the 
streams by becoming itself electrified; but if there 
were a lunar Zodiacal Light, no doubt we could see it 
because of the relative nearness of our satellite. 



IX 

MARVELS OF THE AURORA 

ONE of the most vivid recollections of my early 
boyhood is that of seeing my father return 
hastily into the house one evening and call out to the 
family: "Come outside and look at the sky!" Ours 
was a country house situated on a commanding site, 
and as we all emerged from the doorway we were 
dumfounded to see the heavens filled with pale flames 
which ran Hcking and quivering over the stars. In- 
stantly there sprang into my terrified mind the 
recollection of an awful description of "the Day of 
Judgment" (the Dies Itcb), which I had heard with 
much perturbation of spirit in the Dutch Reformed 
church from the lips of a tall, dark-browed, dreadfully- 
in-earnest preacher of the old-fashioned type. My 
heart literally sank at sight of the spectacle, for it 
recalled the preacher's very words; it was just as he 
had said it would be, and it needed the assured 
bearing of my elders finally to convince me that 

'•That Day of Wrath, O dreadful day, 
When Heaven and Earth shall pass away, 
As David and the Sibyl say," 

had not actually come upon us. And even the older 
members of the household were not untouched with 

144 



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MARVELS OF THE AURORA 

misgivings when menacing spots of crimson appeared, 
breaking out now here, now there, in the shuddering 
sky. Toward the north the spectacle was appalling. 
A huge arch spanned an unnaturally dark segment 
resting on the horizon, and above this arch sprang up 
beams and streamers in a state of incessant agitation, 
sometimes shooting up to the zenith with a velocity 
that took one's breath, and sometimes suddenly fall- 
ing into long ranks, and marching, marching, marching, 
like an endless phalanx of fiery spectres, and moving, 
as I remember, always from east to west. The ab- 
solute silence with which these mysterious evolutions 
were performed and the quavering reflections which 
were thrown upon the ground increased the awfulness 
of the exhibition. Occasionally enormous curtains 
of lambent flame rolled and unrolled with a majestic 
motion, or were shaken to and fro as if by a mighty, 
noiseless wind. At times, too, a sudden billowing 
rush would be made toward the zenith, and for a 
minute the sky overhead would glow so brightly that 
the stars seemed to have been consumed. The spec- 
tacle continued with varying intensity for hours. 

This exhibition occurred in Central New York, 
a latitude in which the Aurora Borealis is seldom seen 
with so much splendor. I remember another similar 
one seen from the city of New York in November, 
1882. On this last occasion some observers saw a 
great upright beam of light which majestically moved 
across the heavens, stalking like an apparition in the 
midst of the auroral pageant, of whose general move- 
ments it seemed to be independent, maintaining always 
its upright posture, and following a magnetic parallel 

147 



CURIOSITIES OF THE SKY 

from east to west. This mysterious beam was seen 
by no less than twenty-six observers in different parts 
of the country, and a comparison of their observations 
led to a curious calculation indicating that the 
apparition was about one hundred and thirty -three 
miles tall and moved at the speed of ten miles per 
second ! 

But, as everybody knows, it is in the Arctic regions 
that the Aurora, or the ** Northern Lights," can best 
be seen. There, in the long polar night, when for 
months together the sun does not rise, the strange 
coruscations in the sky often afford a kind of spectral 
daylight in unison with the weird scenery of the 
world of ice. The pages in the narratives of Arctic 
exploration that are devoted to descriptions of the 
wonderful effects of the Northern Lights are second 
to none that man has ever penned in their fascination. 
The lights, as I have already intimated, display as- 
tonishing colors, particularly shades of red and green, 
as they flit from place to place in the sky. The dis- 
covery that the magnetic needle is affected by the 
Aurora, quivering and darting about in a state of 
extraordinary excitement when the lights are play- 
ing in the sky, only added to the mystery of the 
phenomenon until its electro-magnetic nature had 
been established. This became evident as soon as 
it was known that the focus of the displays was the 
magnetic pole; and when the far South was visited 
the Aurora Australis was found, having its centre at 
the South Magnetic Pole. Then, if not before, it was 
clear that the earth was a great globular magnet, 
having its poles of opposite magnetism, and that 

148 



MARVELS OF THE AURORA 

the auroral lights, whatever their precise cause might 
be, were manifestations of the magnetic activity of our 
planet. After the invention of magnetic telegraphy 
it was found that whenever a great Aurora occurred 
the telegraph lines were interrupted in their opera- 
tion, and the ocean cables ceased to work. Such a 
phenomenon is called a ** magnetic storm." 

The interest excited by the Aurora in scientific 
circles was greatly stimulated when, in the last half 
of the nineteenth century, it was discovered that it is 
a phenomenon intimately associated with disturb- 
ances on the sun. The ancient ** Zurich Chronicles," 
extending from the year looo to the year 1800, in 
which both sun-spots visible to the naked eye and 
great displays of the auroral lights were recorded, 
first set Rudolph Wolf on the track of this discovery. 
The first notable proof of the suspected connection 
was furnished with dramatic emphasis by an oc- 
currence which happened on September i, 1859. 
Near noon on that day two intensely brilliant points 
suddenly broke out in a group of sun-spots which were 
under observation by Mr. R. C. Carrington at his 
observatory at Redhill, England. The points re- 
mained visible for not more than five minutes, during 
which interval they moved thirty-five thousand miles 
across the solar disk. Mr. R. Hodgson happened to 
see the same phenomenon at his observatory at 
Highgate, and thus all possibility of deception was 
removed. But neither of the startled observers could 
have anticipated what was to follow, and, indeed, it 
was an occurrence which has never been precisely 
duplicated. I quote the eloquent account given by 

151 



CURIOSITIES OF THE SKY 

Miss Gierke, in her History of Astronomy During the 
Nineteenth Century. 

"This unique phenomenon seemed as if specially 
designed to accentuate the inference of a sympathetic 
relation between the earth and the sun. From August 
28 to September 4, 1859, a magnetic storm of un- 
paralleled intensity, extent, and duration was in 
progress over the entire globe. Telegraphic com- 
munication was everywhere interrupted — except, in- 
deed, that it was in some cases found practicable to 
work the lines without batteries by the agency of the 
earth-currents alone; sparks issued from the wires; 
gorgeous auroras draped the skies in solemn crimson 
over both hemispheres, and even in the tropics; the 
magnetic needle lost all trace of continuity in its 
movements and darted to and fro as if stricken with 
inexplicable panic. The coincidence was even closer. 
At the very instant of the solar outburst witnessed by 
Carrington and Hodgson the photographic apparatus 
at Kew registered a marked disturbance of all the 
three magnetic elements; while shortly after the en- 
suing midnight the electric agitation culminated, 
thrilling the whole earth with subtle vibrations, and 
lighting up the atmosphere from pole to pole with 
coruscating splendors which perhaps dimly recall the 
times when our ancient planet itself shone as a star." 

If this amazing occurrence stood alone, and as I 
have already said it has never been exactly duplicated, 
doubt might be felt concerning some of the inferences 
drawn from it; but in varying forms it has been re- 
peated many times, so that now hardly any one ques- 
tions the reality of the assumed connection between 

152 



MARVELS OF THE AURORA 

solar outbursts and magnetic storms accompanied by 
auroral displays on the earth. It is true that the late 
Lord Kelvin raised difficulties in the way of the hy- 
pothesis of a direct magnetic action of the sun upon 
the earth, because it seemed to him that an inadmissi- 
ble quantity of energy was demanded to account for 
such action. But no calculation like that which he 
made is final, since all calculations depend upon the 
validity of the data ; and no authority is unshakable in 
science, because no man can possess omniscience. It 
was Lord Kelvin who, but a few years before the 
thing was actually accomplished, declared that aerial 
navigation was an impracticable dream, and demon- 
strated its impracticability by calculation. However 
the connection may be brought about, it is as certain 
as evidence can make it that solar outbursts are coin- 
cident with terrestrial magnetic disturbances, and 
coincident in such a way as to make the inference of a 
causal connection irresistible. The sun is only a little 
more than a hundred times its own diameter away 
from the earth. Why, then, with the subtle connection 
between them afforded by the ether which conveys 
to us the blinding solar light and the life-sustaining 
solar heat, should it be so difficult to believe that the 
sun's enormous electric energies find a way to us also ? 
No doubt the impulse coming from the sun acts upon 
the earth after the manner of a touch upon a trigger, 
releasing energies which are already stored up in our 
planet. 

But besides the evidence afforded by such occur- 
rences as have been related of an intimate connection 
between solar outbreaks and terrestrial magnetic 

153 



CURIOSITIES OF THE SKY 

flurries, attended by magnificent auroral displays, 
there is another line of proof pointing in the same 
direction. Thus, it is known that the sun-spot period, 
as remarked in a preceding chapter, coincides in a 
most remarkable manner with the periodic fluctua- 
tions in the magnetic state of the earth. This coin- 
cidence runs into the most astonishing details. For 
instance, when the sun-spot period shortens, the 
auroral period shortens to precisely the same extent; 
as the short sun-spot periods usually bring the most in- 
tense outbreaks of solar activity, so the corresponding 
short auroral periods are attended by the most violent 
magnetic storms; a secular period of about two 
hundred and twenty-two years affecting sun-spots is 
said to have its auroral duplicate ; a shorter period of 
fifty-five and a half years, which some observers be- 
lieve that they have discovered appears also to be com- 
mon to the two phenomena; and yet another *' super- 
posed" period of about thirty-five years, which some 
investigators aver exists, affects sun-spots and auroras 
alike. In short, the coincidences are so numerous 
and significant that one would have to throw the 
doctrine of probability to the winds in order to be 
able to reject the conclusion to which they so plainly 
lead. 

But still the question recurs: How is the influence 
transmitted ? Here Arrhenius comes once more with 
his hypothesis of negative corpuscles, or ions, driven 
away from the sun by light-pressure — a hypothesis 
which seems to explain so many things — and offers 
it also as an explanation of the way in which the sun 
creates the Aurora. He would give the Aurora the 

154 



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MARVELS OF THE AURORA 

same lineage with the Zodiacal Light. To under- 
stand the application of this theory we must first 
recall the fact that the earth is a great magnet having 
its two opposite poles of magnetism, one near the 
Arctic and the other near the Antarctic Circle. Like 
all magnets, the earth is surrounded with ** lines of 
force," which, after the manner of the curved rays we 
saw in the photograph of a solar eclipse, siart from 
a pole, rising at first nearly vertically, then bend 
gradually over, passing high above the equator, and 
finally descending in converging sheaves to the 
opposite pole. Now the axis of the earth is so 
placed in space that it lies at nearly a right angle to 
the direction of the sun, and as the streams of nega- 
tively charged particles come pouring on from the 
sun (see the last preceding chapter), they arrive in 
the greatest numbers over the earth's equatorial 
regions. There they encounter the lines of magnetic 
force at the place where the latter have their greatest 
elevation above the earth, and where their direction 
is horizontal to the earth's surface. Obeying a law 
which has been demonstrated in the laboratory, the 
particles then follow the lines of force toward the 
poles. While they are above the equatorial regions 
they do not become luminescent, because at the great 
elevation that they there occupy there is virtually 
no atmosphere ; but as they pass on toward the north 
and the south they begin to descend with the lines of 
force, curving down to meet at the poles; and, en- 
countering a part of the atmosphere comparable in 
density with what remains in an exhausted Crookes 
tube, they produce a glow of cathode rays. This glow 

157 



CURIOSITIES OF THE SKY 

is conceived to represent the Aurora, which may 
consequently be likened to a gigantic exhibition of 
vacuum-tube lights. Anybody who recalls his student 
days in the college laboratory and who has witnessed 
a display of Northern Lights will at once recognize 
the resemblance between them in colors, forms, and 
behavior. This resemblance had often been noted 
before Arrhenius elaborated his hypothesis. 

Without intending to treat his interesting theory 
as more than a possibly correct explanation of the 
phenomena of the Aurora, we may call attention to 
some apparently confirmatory facts. One of the 
most striking of these relates to a seasonal variation 
in the average number of aurorae. It has been ob- 
served that there are more in March and September 
than at any other time of the year, and fewer in June 
and December; moreover (and this is a delicate test 
as applied to the theory), they are slightly rarer in 
June than in December. Now all these facts seem 
to find a ready explanation in the hypothesis of Ar- 
rhenius, thus: (i) The particles issuing from the sun 
are supposed to come principally from the regions 
whose excitement is indicated by the presence of 
sun-spots (which accords with Hale's observation that 
sun-spots are columns of ionized vapors), and these 
regions have a definite location on either side of the 
solar equator, seldom approaching it nearer than 
within 5° or io° north or south, and never extending 
much beyond 35° toward either pole; (2) The equator 
of the sun is inclined about 7° to the plane of the 
earth's orbit, from which it results that twice in a 
year — viz., in June and December — ^the earth is directly 

158 



MARVELS OF THE AURORA 

over the solar equator, and twice a year — viz., in 
March and September — ^when it is farthest north or 
south of the solar equator, it is over the inner edge 
of the sun-spot belts. Since the corpuscles must be 
supposed to be propelled radially from the sun, few 
will reach the earth when the latter is over the solar 
equator in June and December, but when it is over, 
or nearly over, the spot belts, in March and September, 
it will be in the line of fire of the more active parts 
of the solar surface, and relatively rich streams of 
particles will reach it. This, as will be seen from 
what has been said above, is in strict accord with the 
observed variations in the frequency of aurorae. 
Even the fact that somewhat fewer auroras are seen 
in June than in December also finds its explanation 
in the known fact that the earth is about three million 
miles nearer the sun in the winter than in the summer, 
and the number of particles reaching it will vary, 
like the intensity of light, inversely as the square of 
the distance. These coincidences are certainly very 
striking, and they have a cumulative force. If we 
accept the theory, it would appear that we ought to 
congratulate ourselves that the inclination of the 
sun's equator is so slight, for as things stand the 
earth is never directly over the most active regions 
of the sun-spots, and consequently never suffers from 
the maximum bombardment of charged particles of 
which the sun is capable. Incessant auroral dis- 
plays, with their undulating draperies, flitting colors, 
and marching columns might not be objectionable 
from the point of view of picturesqueness, but one 
magnetic storm of extreme intensity following closely 

^ 159 



CURIOSITIES OF THE SKY 

Upon the heels of another, for months on end, crazing 
the magnetic needle and continually putting the 
telegraph and cable lines out of commission, to say 
nothing of their effect upon "wireless telegraphy," 
would hardly add to the charms of terrestrial exist- 
ence. 

One or two other curious points in connection with 
Arrhenius' hypothesis may be mentioned. First, 
the number of auroras, according to his explanation, 
ought to be greatest in the daytime, when the face 
of the earth on the sunward side is directly exposed 
to the atomic bombardment. Of course visual ob- 
servation can give us no information about this, since 
the light of the Aurora is never sufficiently intense to 
be visible in the presence of daylight, but the records 
of the magnetic observatories can be, and have been, 
appealed to for information, and they indicate that 
the facts actually accord with the theory. Behind 
the veil of sunlight in the middle of the afternoon, 
there is good reason to believe, auroral exhibitions 
often take place which would eclipse in magnificence 
those seen at night if we could behold them. Ob- 
servation shows, too, that auroras are more frequent 
before than after midnight, which is just what we 
should expect if they originate in the way that 
Arrhenius supposes. Second, the theory offers an ex- 
planation of the alleged fact that the formation of 
clouds in the upper air is more frequent in years when 
aurorse are most abundant, because clouds are the 
result of the condensation of moisture upon floating 
particles in the atmosphere (in an absolutely dustless 
atmosphere there would be no clouds), and it has been 

1 60 



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MARVELS OF THE AURORA 

proved that negative ions like those supposed to come 
from the sun play a master part in the phenomena of 
cloud formation. 

Yet another singular fact, almost mystical in its 
suggestions, may be mentioned. It seems that the 
dance of the auroral lights occurs most frequently 
during the absence of the moon from the hemisphere 
in which they appear, and that they fiee, in greater 
part, to the opposite hemisphere when the moon's 
revolution in an orbit considerably inclined to the 
earth's equator brings her into that where they have 
been performing. Arrhenius himself discovered this 
curious relation of auroral frequency to the position 
of the moon north or south of the equator, and he 
explains it in this way: The moon, like the earth, is 
exposed to the influx of the ions from the sun; but 
having no atmosphere, or almost none, to interfere 
with them, they descend directly upon her surface 
and charge her with an electric negative potential to a 
very high degree. In consequence of this she affects 
the electric state of the upper parts of the earth's 
atmosphere where they lie most directly beneath her, 
and thus prevents, to a large extent, the negative 
discharges to which the appearance of the Aurora is 
due. And so ''the extravagant and erring spirit" 
of the Aurora avoids the moon as Hamlet's ghost 
fled at the voice of the cock announcing the awakening 
of the god of day. 

There are even other apparent confirmations 
of the hypothesis, but we need not go into them. 
We shall, however, find one more application of it 
in the next chapter, for it appears to be a kind of cure- 

163 



CURIOSITIES OF THE SKY 

all for astronomical troubles; at any rate, it offers 
a conceivable solution of the question, How does 
the sun manage to transmit its electric influence to 
the earth ? And this solution is so grandiose in con- 
ception, and so novel in the mental pictures that it 
offers, that its acceptance would not in the least de- 
tract from the impression that the Aurora makes 
upon the imagination. 



X 

STRANGE ADVENTURES OF COMETS 

THE fears and legends of ancient times before 
Science was born, and the superstitions of the 
Dark Ages, sedulously cultivated for theological pur- 
poses by monks and priests, have so colored our ideas 
of the influence that comets have had upon the 
human mind that many readers may be surprised to 
learn that it was the apparition of a wonderful comet, 
that of 1843, which led to the foundation of our 
greatest astronomical institution, the Harvard College 
Observatory. No doubt the comet superstition exist- 
ed half a century ago, as, indeed, it exists yet to-day, 
but in this case the marvellous spectacle in the sky 
proved less effective in inspiring terror than in awaken- 
ing a desire for knowledge. Even in the sixteenth 
century the views that enlightened minds took of 
comets tended powerfully to inspire popular con- 
fidence in science, and Halley's prediction, after seeing 
and studying the motion of the comet which ap- 
peared in 1682, that it would prove to be a regular 
member of the sun's family and would be seen re- 
turning after a period of about seventy-six years, to- 
gether with the fulfilment of that prediction, pro- 
duced a revulsion from the superstitious notions 
which had so long prevailed. 

165 



CURIOSITIES OF THE SKY 

Then the facts were made plain that comets are 
subject to the law of gravitation equally with the 
planets; that there are many which regularly return 
to the neighborhood of the sun (perihelion) ; and that 
these travel in orbits differing from those of the 
planets only in their greater eccentricity, alt ough 
they have the peculiarity that they do not, Hke the 
planets, all go round the sun in the same direction, 
and do not keep within the general plane of the 
planetary system, but traverse it sometimes from 
above and sometimes from below. Other comets, 
including most of the "great" ones, appear to travel 
in parabolic or, in a few cases, hyperbolic orbits, 
which, not being closed curves, never bring them back 
again. But it is not certain that these orbits may not 
be extremely eccentric ellipses, and that after the 
lapse of hundreds, or thousands, of years the comets 
that follow them may not reappear. The question 
is an interesting one, because if all orbits are really 
ellipses, then all comets must be permanent members 
of the solar system, while in the contrary case many 
of them are simply visitors, seen once and never to 
be seen again. The hypothesis that comets are 
originally interlopers might seem to derive some 
support from the fact that the certainly periodic ones 
are associated, in groups, with the great outer planets, 
whose attraction appears to have served as a trap 
for them by turning them into elliptical orbits and 
thus making them prisoners in the solar system. 
Jupiter, owing to his great mass and his commanding 
situation in the system, is the chief "comet-catcher"; 
but he catches them not for himself, but for the sun. 

i66 




swift's comet, taken at arequipa, march 30, 1892 



STRANGE ADVENTURES OF COMETS 

Yet if comets do come originally from without the 
borders of the planetary system, it does not, by any 
means, follow that they were wanderers at large in 
space before they yielded to the overmastering at- 
traction of the sun. Investigation of the known 
cometary orbits, combined with theoretical con- 
siderations, has led some astronomers to the con- 
clusion that as the sun travels onward through space 
he ''picks up en route'* cometary masses which, with- 
out belonging strictly to his empire, are borne along 
in the same vast ''cosmical current" that carries the 
solar system. 

But while no intelligent person any longer thinks 
that the appearance of a great comet is a token from 
the heavenly powers of the approaching death of a 
mighty ruler, or the outbreak of a devastating war, 
or the infliction of a terrible plague upon wicked man- 
kind, science itself has discovered mysteries about 
comets which are not less fascinating because they are 
more intellectual than the irrational fancies that they 
have displaced. To bring the subject properly be- 
fore the mind, let us see what the principal phenomena 
connected with a comet are. 

At the present day comets are ordinarily ''picked 
up" with the telescope or the photographic plate be- 
fore any one except their discoverer is aware of their 
existence, and usually they remain so insignificant 
in appearance that only astronomers ever see them. 
Yet so great is the prestige of the word "comet" 
that the discovery of one of these inconspicuous wan- 
derers, and its subsequent movements, become items 
of the day's news which everybody reads with the 

169 



CURIOSITIESOFTHE SKY 

feeling, perhaps, that at least he knows what is going 
on in the universe even if he doesn't understand it. 
But a truly great comet presents quite a different prop- 
osition. It, too, is apt to be detected coming out of 
the depths of space before the world at large can get 
a glimpse of it, but as it approaches the sun its aspect 
undergoes a marvellous change. Agitated apparently 
by solar influence, it throws out a long streaming tail 
of nebulous light, directed away from the sun and 
looking as if blown out like a pennon by a powerful 
wind. Whatever may be the position of the comet 
with regard to the sun, as it circles round him it con- 
tinually keeps its tail on the off side. This, as we shall 
soon see, is a fact of capital importance in relation to 
the probable nature of comets' tails. Almost at the 
same time that the formation of the tail is observed 
a remarkable change takes place in the comet's head, 
which, by the way, is invariably and not merely 
occasionally its most important part. On approach- 
ing the sun the head usually contracts. Coincidently 
with this contraction a nucleus generally makes its 
appearance. This is a bright, star-like point in the 
head, and it probably represents the totality of solid 
matter that the comet possesses. But it is regarded 
as extremely unlikely that even the nucleus consists 
of a uniformly solid mass. If it were such, comets 
would be far more formidable visitors when they pass 
near the planets than they have been found to be. 
The diameter of the nucleus may vary from a few 
hundred up to several thousand miles; the heads, on 
the average, are from twenty-five thousand to one 
hundred thousand miles in diameter, although a few 

170 



STRANGE ADVENTURES OF COMETS 

have greatly exceeded these dimensions ; that of the 
comet of 1811, one of the most stupendou'= ever seen, 
was a milHon and a quarter miles in diameter! As to 
the tails, notwithstanding their enormous length — 
some have been more than a hundred million miles 
long — ^there is reason to believe that they are of 
extreme tenuity, ''as rare as vacuum." The smallest 
stars have been seen shining through their most 
brilliant portions with undiminished lustre. 

After the nucleus has been formed it begins to 
throw out bright jets directed toward the sun. A 
stream, and sometimes several streams, of light also 
project sunward from the nucleus, occasionally ap- 
pearing like a stunted tail directed oppositely to the 
real tail. Symmetrical envelopes which, seen in 
section, appear as half circles or parabolas, rise sun- 
ward from the nucleus, forming a concentric series. 
The ends of these stream backward into the tail, to 
which they seem to supply material. Ordinarily the 
formation of these ejections and envelopes is attended 
by intense agitation of the nucleus, which twists and 
turns, swinging and gyrating with an appearance 
of the greatest violence. Sometimes the nucleus is 
seen to break up into several parts. The entire heads 
of some comets have been split asunder in passing 
close around the sun; the comet of 1882 retreated into 
space after its perihelion passage with five heads in- 
stead of the one that it had originally, and each of 
these heads had its own tail! 

The possession of the spectroscope has enabled 
astronomers during later years to study the chemical 
composition of comets by analyzing their light. At 

171 



CURIOSITIES OF. THE SKY 

first the only substances thus discovered in them were 
hydro-carbon compounds, due evidently to the 
gaseous envelopes in which some combination of 
hydrogen with carbon existed. Behind this gaseous 
spectrum was found a faint continuous spectrum 
ascribed to the nucleus, which apparently both re- 
flects the sunlight and gives forth the light of a glow- 
ing solid or liquid. Subsequently sodium and iron 
lines were found in cometary spectra. The presence 
of iron would seem to indicate that some of these 
bodies may be much more massive than observations 
on their attractive effects have indicated. In some 
recent comets, such as Morehouse's, in 1908, several 
lines have been found, the origin of which is unknown. 
Without going back of the nineteenth century we 
may find records of some of the most extraordinary 
comets that man has ever looked upon. In 181 1, 
still spoken of as "the year of the comet," because of 
the wonderful vintage ascribed to the skyey visitor, a 
comet shaped like a gigantic sword amazed the whole 
world, and, as it remained visible for seventeen months, 
was regarded by superstitious persons as a symbol 
of the fearful happenings of Napoleon's Russian 
campaign. This comet, the extraordinary size of 
whose head, greatly exceeding that of the sun itself, 
has already been mentioned, was also remarkable for 
exhibiting so great a brilliancy without approaching 
even to the earth's distance from the sun. But there 
was once a comet (and only once — in the year 1729) 
which never got nearer to the sun than four times the 
distance of the earth and yet appeared as a formid- 
able object in the sky. As Professor Young has re- 

172 



STRANGE ADVENTURES OF COMETS 

marked, ''it must have been an enormous comet to 
be visible from such a distance." And we are to 
remember that there were no great telescopes in the 
year 1729. That comet affects the imagination like 
a phantom of space peering into the solar system, dis- 
playing its enormous train afar off (which, if it had 
approached as near as other comets, would probably 
have become the celestial wonder of all human 
memory) , and then turning away and vanishing in the 
depths of immensity. 

In 1843 ^ comet appeared which was so brilliant 
that it could be seen in broad day close beside the 
sun! This was the first authenticated instance of 
that kind, but the occurrence was to be repeated, as 
we shall see in a moment, less than forty years later. 

The splendid comet of 1858, usually called Donati's, 
is remembered by many persons yet living. It was, 
perhaps, both as seen by the naked eye and with the 
telescope, the most beautiful comet of which we have 
any record. It too marked a rich vintage year, still 
remembered in the vineyards of France, where there 
is a popular belief that a great comet ripens the grape 
and imparts to the wine a flavor not attainable by 
the mere skill of the cultivator. There are ''comet 
wines," carefully treasured in certain cellars, and 
brought forth only when their owner wishes to treat 
his guests to a sip from paradise. 

The year 1861 saw another very remarkable comet, 
of an aspect strangely vast and diffuse, which is 
believed to have swept the earth with its immense 
tail when it passed between us and the sun on the 
night of June 30th, an event which produced no other 

173 



CURIOSITIES OF THE SKY 

known effect than the appearance of an unwonted 
amount of scattered light in the sky. 

The next very notable comet was the "Great 
Southern Comet" of 1880, which was not seen from 
the northern hemisphere. It mimicked the aspect 
of the famous comet of 1843, and to the great sur- 
prise of astronomers appeared to be travelling in the 
same path. This proved to be the rising of the 
curtain for an astronomical sensation unparalleled in 
its kind; for two years later another brilliant comet 
appeared, first in the southern hemisphere, and it too 
followed the same track. The startling suggestion was 
now made that this comet was identical with those 
of 1843 and 1880, its return having been hastened by 
the resistance experienced in passing twice through the 
coronal envelope, and there were some who thought 
that it would now swing swiftly round and then 
plunge straight into the sun, with consequences that 
might be disastrous to us on account of the "flash 
of heat'* that would be produced by the impact. 
Nervous people were frightened, but observation soon 
proved that the danger was imaginary, for although 
the comet almost grazed the sun, and must have 
rushed through two or three million miles of the 
coronal region, no retardation of its immense velocity 
was perceptible, and it finally passed away in a 
damaged condition, as before remarked, and has never 
since appeared. 

Then the probable truth was perceived — viz., that 
the three comets (1843, 1880, and 1882) were not 
one identical body, but three separate ones all travel- 
ling in the same orbit. It was found, too, that a 

174 



STRANGE ADVENTURES OF COMETS 

comet seen in 1668 bore similar insignia of relation- 
ship. The natural inference was that these four 
bodies had once formed a single mass which had 
been split apart by the disruptive action of the sun. 
Strength was lent to this hypothesis by the fact that 
the comet of 1882 was apparently torn asunder dur- 
ing its perihelion passage, retreating into space in a 
dissevered state. But Prof. George Forbes has a 
theory that the splitting of the original cometary mass 
was effected by an unknown planet, probably greater 
than Jupiter, situated at a hundred times the earth's 
distance from the sun, and revolving in a period of a 
thousand years. He supposes that the original comet 
was not that of 1668, but one seen in 1556, which has 
since been ''missing," and that its disruption occurred 
from an encounter with the supposititious planet 
about the year 1700. Truly from every point of view 
comets are the most extraordinary of adventurers! 

The comet of 1882 was likewise remarkable for 
being visible, like its predecessor of 1843, i^ Ml day- 
light in close proximity to the sun. The story of its 
detection when almost in contact with the solar disk 
is dramatic. It had been discovered in the southern 
hemisphere only a couple of weeks before its perihelion, 
which occurred on September 17th, and on the fore- 
noon of that day it was seen by Doctor Common in 
England, and by Doctor Elkin and Mr. Finlay at the 
Cape of Good Hope, almost touching the sun. It 
looked like a dazzling white bird with outspread 
wings. The southern observers watched it go right 
into the sun, when it instantly disappeared. What 
had happened was that the comet in passing its 

175 



CURIOSITIES OF THE SKY 

perihelion point had swung exactly between the earth 
and the sun. On the following morning it was seen 
from all parts of the world close by the sun on the 
opposite side, and it remained thus visible for three 
days, gradually receding from the solar disk. It then 
became visible for northern observers in the morning 
sky before sunrise, brandishing a portentous sword- 
shaped tail which, if it had been in the evening sky, 
would have excited the wonder of hundreds of millions, 
but situated where it was, comparatively few ever sav/ it. 
The application of photography to the study of 
comets has revealed many curious details which 
might otherwise have escaped detection, or at best 
have remained subject to doubt. It has in particular 
shown not only the precise form of the tails, but the 
remarkable vicissitudes that they undergo. Professor 
Barnard's photographs of Brooks' comet in 1893 
suggested, by the extraordinary changes in the form 
of the tail which they revealed, that the comet was 
encountering a series of obstructions in space which 
bent and twisted its tail into fantastic shapes. The 
reader will observe the strange form into which the 
tail was thrown on the night of October 21st. A 
cloud of meteors through which the comet was passing 
might have produced such deformations of its tail. 
In the photograph of Daniels' comet of 1907, a curious 
striping of the tail will be noticed. The short bright 
streaks seen in the photograph, it may be explained, 
are the images of stars which are drawn out into lines 
in consequence of the fact that the photographic 
telescope was adjusted to follow the motion of the 
comet while the stars remained at rest. 

176 




DANIELS COMET. AUGUST II, 1907 



STRANGE ADVENTURES OF COMETS 

But the adventures of comets are not confined to 
possible encounters with unknown obstacles. We 
have referred to the fact that the great planets, and 
especially Jupiter, frequently interfere with the 
motions of comets. This interference is not limited to 
the original alteration of their orbits from possible 
parabolas to ellipses, but is sometimes exercised again 
and again, turning the bewildered comets into 
elliptical paths of all degrees of eccentricity. A 
famous example of this kind of planetary horse-play 
is furnished by the story of Lexell's missing comet. 
This comet was first seen in 1770. Investigation 
showed that it was moving in an orbit which should 
bring it back to perihelion every five and a half years ; 
yet it had never been seen before and, although often 
searched for, has never been seen since. Laplace and 
Leverrier proved mathematically that in 1767 it 
had approached so close to Jupiter as to be involved 
among the orbits of his satellites. What its track 
had been before is not known, but on that occasion the 
giant planet seized the interloper, threw it into a short 
elliptic orbit, and sent it, like an arrested vagrant, to 
receive sentence at the bar of the sun. On this 
journey it passed within less than 1,500,000 miles of 
the earth. The form of orbit which Jupiter had im- 
pressed required, as we have said, its return in about 
five and a half years; but soon after 1770 it had the 
misfortune a second time to encounter Jupiter at 
close range, and he, as if dissatisfied with the leniency 
of the sun, or indignant at the stranger's familiarity, 
seized the comet and hurled it out of the system, or 
at any rate so far away that it has never since been 

179 



CURIOSITIES OF THE SKY 

able to rejoin the family circle that basks in the 
immediate rays of the solar hearth. Nor is this the 
only instance in which Jupiter has dealt summarily 
with small comets that have approached him with 
too little deference. 

The function which Jupiter so conspicuously ful- 
fils as master of the hounds to the sun is worth con- 
sidering a little more in detail. To change the figure, 
imagine the sun in its voyage through space to be 
like a majestic battleship surrounded by its scouts. 
Small vessels (the comets), as they are overhauled 
by the squadron, are taken in charge by the scouts, 
with Jupiter for their chief, and are forced to accom- 
pany the fleet; but not all are impressed. If a strange 
comet undertakes to run across Jupiter's bows the 
latter brings it to, and makes prize of it by throwing 
it into a relatively small ellipse with the sun for its 
focus. Thenceforth, unless, as happened to the un- 
happy comet of Lexell, it encounters Jupiter again 
in such a way as to be diverted by him into a more 
distant orbit, it can never get away. About thirty 
comets are now known to have thus been captured 
by the great planet, and they are called ** Jupiter's 
Comet Family." But, on the other hand, if a wan- 
dering comet crosses the wake of the chief planetary 
scout the latter simply drives it away by accelerating 
its motion and compels it to steer off into open space. 
The transformation of comets into meteors will be 
considered in the next chapter, but here, in passing, 
mention may be made of the strange fate of one mem- 
ber of Jupiter's family, Biela's comet, which, having 
become overbold in its advances to its captor, was, 

1 80 



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STRANGE ADVENTURES OF COMETS 

after a few revolutions in its impressed orbit, torn to 
pieces and turned into a flock of meteors. 

And now let us return to the mystery of comets' 
tails. That we are fully justified in speaking of the 
tails of comets as mysterious is proved by the dec- 
laration of Sir John Herschel, who averred, in so 
many words, that ' ' there is some profound secret and 
mystery of nature concerned in this phenomenon," 
and this profound secret and mystery has not yet been 
altogether cleared up. Nevertheless, the all-explain- 
ing hypothesis of Arrhenius offers us once more a 
certain amount of aid. Comets' tails, Arrhenius 
assures us, are but another result of the pressure of 
light. The reader will recall the applications of this 
theory to the Zodiacal Light and the Aurora. In the 
form in which we now have to deal with it, the sup- 
position is made that as a comet approaches the sun 
eruptions of vapor, due to the solar heat, occur in its 
nucleus. These are naturally most active on the 
side which is directly exposed to the sun, whence the 
appearance of the immense glowing envelopes that 
surround the nucleus on the sunward side. Among the 
particles of hydro-carbon, and perhaps solid carbon 
in the state of fine dust, which are thus set free there 
will be many whose size is within the critical limit 
which enables the light-waves from the sun to drive 
them away. Clouds of such particles, then, will 
stream off behind the advancing comet, producing the 
appearance of a tail. This accounts for the fact that 
the tails of comets are always directed away from 
the sun, and it also explains the varying forms of the 
tails and the extraordinary changes that they undergo. 

183 



10 



CURIOSITIES OF THE SKY 

The speed of the particles driven before the light- 
waves must depend upon their size and weight, the 
lightest of a given size travelling the most swiftly. 
By accretion certain particles might grow, thus losing 
velocity and producing the appearance of bunches 
in the tail, such as have been observed. The hypoth- 
esis also falls in with the researches of Bredichin, 
who has divided the tails of comets into three principal 
classes — viz.: (i) Those which appear as long, straight 
rays; (2) Those which have the form of curved plum.es 
or scimitars; (3) Those which are short, brushy, and 
curved sharply backward along the comet's path. 
In the first type he calculates the repulsive force at 
from twelve to fifteen times the force of gravity; in 
the second at from two to four times; and in the 
third at about one and a half times. The straight 
tails he ascribes to hydrogen because the hydrogen 
atom is the lightest known; the sword-shaped tails 
to hydro-carbons; and the stumpy tails to vaporized 
iron. It will be seen that, if the force driving off the 
tails is that which Arrhenius assumes it to be, the 
forms of those appendages would accord with those 
that Bredichin's theory calls for. At the same time 
we have an explanation of the multiple tails with which 
some comets have adorned themselves. The comet 
of 1744, for instance, had at one time no less than 
seven tails spread in a wide curved brush behind it. 
Donati's comet of 1858 also had at least two tails, 
the principal one sword-shaped and the other long, 
narrow, and as straight as a rule. According to Bred- 
ichin, the straight tail must have been composed of 
hydrogen, and the other of some form of hydro-carbon 

184 



STRANGE ADVENTURES OF COMETS 

whose atoms are heavier than those of hydrogen, and, 
consequently, when swept away by the storm of hght- 
waves, followed a curvature depending upon the 
resultant of the forces operating upon them. The 
seven tails of the comet of 1744 presented a kind of 
diagram graphically exhibiting its complex composi- 
tion, and, if we knew a little more about the con- 
stituents of a comet, we might be able to say from 
the amount of curvature of the different tails just 
what were the seven substances of which that comet 
consisted. 

If these theories seem to the reader fantastic, at 
any rate they are no more fantastic than the phenom- 
ena that they seek to explain. 



XI 

METEORS, FIRE-BALLS, AND METEORITES 

ONE of the most terrorizing spectacles with which 
the heavens have ever caused the hearts of men 
to quake occurred on the night of November 13, 1833. 
On that night North America, which faced the storm, 
was under a continual rain of fire from about ten 
o'clock in the evening until daybreak. 

The fragments of a comet had struck the earth. 

But the meaning of what had happened was not 
discovered until long afterward. To the astronomers 
who, with astonishment not less than that of other 
people, watched the wonderful scene, it was an un- 
paralleled ''shower of meteors." They did not then 
suspect that those meteors had once formed the head 
of a comet. Light dawned when, a year later, Prof. 
Denison Olmstead, of Yale College, demonstrated that 
the meteors had all moved in parallel orbits around 
the sun, and that these orbits intersected that of the 
earth at the point where our planet happened to be 
on the memorable night of November 13th. Professor 
Olmstead even went so far as to suggest that the 
cloud of meteors that had encountered the earth 
might form a diffuse comet ; but full recognition of the 
fact that they were cometary d6bris came later, as 

186 



METEORS, FIRE-BALLS, METEORITES 

the result of further investigation. The key to the 
secret was plainly displayed in the spectacle itself, 
and was noticed without being understood by thou- 
sands of the terror-stricken beholders. It was an 
umbrella of fire that had opened overhead and covered 
the heavens ; in other words, the meteors all radiated 
from a particular point in the constellation Leo, and, 
being countless as the snowfiakes in a winter tempest, 
they ribbed the sky with fiery streaks. Professor 
Olmstead showed that the radiation of the meteors 
from a fixed point was an effect of perspective, and 
in itself a proof that they were moving in parallel 
paths when they encountered the earth. The fact 
was noted that there had been a similar, but in- 
comparably less brilliant, display of meteors on the 
same day of November, 1832, and it was rightly con- 
cluded that these had belonged to the same stream, 
although the true relationship of the phenomena was 
not immediately apprehended. Olmstead ascribed 
to the meteors a revolution about the sun once in 
every six months, bringing them to the intersection 
of their orbit with that of the earth every November 
13th; but later investigators found that the real 
period was about thirty-three and one-quarter years, 
so that the great displays were due three times in a 
century, and their return was confidently predicted 
for the year 1866. The appearance of the meteors 
in 1832, a year before the great display, was ascribed 
to the great length of the stream which they formed 
in space — so great that they required more than two 
years to cross the earth's orbit. In 1832 the earth had 
encountered a relatively rare part of the stream, 

187 



CURIOSITIES OF THE SKY 

but in 1833, on returning to the crossing-place, it 
found there the richest part of the stream pouring 
across its orbit. This explanation also proved to be 
correct, and the predicted return in 1866 was duly 
witnessed, although the display was much less brilliant 
than in 1833. It was followed by another in 1867. 

In the mean time Olmstead's idea of a cometary 
relationship of the meteors was demonstrated to be 
correct by the researches of Schiaparelli and others, 
who showed that not only the November meteors, but 
those of August, which are seen more or less abun- 
dantly every year, travelled in the tracks of well- 
known comets, and had undoubtedly an identical 
origin with those comets. In other words the comets 
and the meteor-swarms were both remnants of original 
masses which had probably been split up by the action 
of the sun, or of some planet to which they had made 
close approaches. The annual periodicity of the 
August meteors was ascribed to the fact that the 
separation had taken place so long ago that the 
meteors had become distributed all around the orbit, 
in consequence of which the earth encountered 
some of them every year when it arrived at the 
crossing - point. Then Lever rier showed that the 
original comet associated with the November meteors 
was probably brought into the system by the influence 
of the planet Uranus in the year 126 of the Christian 
era. Afterward Alexander Herschel identified the 
tracks of no less than seventy-six meteor - swarms 
(most of them inconspicuous) with those of comets. 
The still more recent researches of Mr. W. F. Denning 
make it probable that there are no meteors which 

188 



M *^, 



G 

2 

O 

o 

O 



:2. I-' 

M 

> 
w 




METEORS, FIRE-BALLS, METEORITES 

do not belong to a flock or system probably formed 
by the disintegration of a cometary mass; even the 
apparently sporadic ones which shoot across the sky, 
"lost souls in the night," being members of flocks 
which have become so widely scattered that the earth 
sometimes takes weeks to pass through the region of 
space where their paths lie. 

The November meteors should have exhibited an- 
other pair of spectacles in 1899 and 1900, and their 
failure to do so caused at first much disappointment, 
until it was made plain that a good reason existed 
for their absence. It was found that after their last 
appearance, in 1867, they had been disturbed in their 
movements by the planets Jupiter and Saturn, whose 
attractions had so shifted the position of their orbit 
that it no longer intersected that of the earth, as it 
did before. Whether another planetary interference 
will some time bring the principal mass of the Novem- 
ber meteors back to the former point of intersection 
with the earth's orbit is a question for the future to 
decide. It would seem that there may be several 
parallel streams of the November meteors, and that 
some of them, like those of August, are distributed 
entirely around the orbit, so that every mid-November 
we see a few of them. 

We come now to a very remarkable example of the 
disintegration of a comet and the formation of a 
meteor - stream. In 1826 Biela, of Josephstadt, 
Austria, discovered a comet to which his name was 
given. Calculation showed that it had an orbital 
period of about six and a half years, belonging to 
Jupiter *s "family." On one of its returns, in 1846, 

191 



CURIOSITIES OF THE SKY 

it astonished its watchers by suddenly splitting in two. 
The two comets thus formed out of one separated to 
a distance of about one hundred and sixty thousand 
miles, and then raced side by side, sometimes with a 
curious ligature connecting them, like Siamese twins, 
until they disappeared together in interplanetary 
space. In 1852 they came back, still nearly side by 
side; but now the distance between them had in- 
creased to a million and a quarter of miles. After 
that, at every recurrence of their period, astronomers 
looked for them in vain, until 1872, when an amazing 
thing happened. On the night of November 28th, 
when the earth was crossing the plane of the orbit of 
the missing comet, a brilliant shower of meteors 
burst from the northern sky, travelling nearly in the 
track which the comet should have pursued. The 
astronomers were electrified. Klinkerfues, of Gottin- 
gen, telegraphed to Pogson, of Madras: ''Biela touched 
earth; search near Theta Centauri.'' Pogson searched 
in the place indicated and saw a cometary mass re- 
treating into the southern heavens, where it was soon 
swallowed from sight! 

Since then the Biela meteors have been among the 
recognized periodic spectacles of the sky, and few if 
any doubt that they represent a portion of the missing 
comet whose disintegration began with the separation 
into two parts in 1846. The comet itself has never 
since been seen. The first display of these meteors, 
sometimes called the ''Andromedes," because they 
radiate from the constellation Andromeda, was re- 
markable for the great brilliancy of many of the fire- 
balls that shot among the shower of smaller sparks, 

192 



SECTION OF THE ATMOSPHERE UP TO 
lOO KILOMETERS 

Showing the mean elevation at 
which meteorites and meteors make 
their appearance. Below are shown 
the elevation of Mount Everest; the 
highest manned balloon ascent by 
M. Berson; the height of cirrus clouds; 
the highest free balloon ascent; and 
the elevation attained by the clouds 
of fire-dust ejected by the Krakatoa 
eruption in 1883. (From La Nature.) 






METEORS, FIRE-BALLS, METEORITES 

some of which were described as equalling the full 
moon in size. None of them is known to have reached 
the earth, but during the display of the same meteors 
in 1885 a meteoric mass fell at Mazapil in Northern 
Mexico (it is now in the Museum at Vienna), which 
many have thought may actually be a piece of the 
original comet of Biela. This brings us to the second 
branch of our subject. 

More rare than meteors or falling stars, and more 
startling, except that they never appear in showers, 
are the huge balls of fire which occasionally dart 
through the sky, lighting up the landscapes beneath 
with their glare, leaving trains of sparks behind them, 
often producing peals of thunder when they explode, 
and in many cases falling upon the earth and burying 
themselves from a few inches to several feet in the 
soil, from which, more than once, they have been 
picked up while yet hot and fuming. These balls 
are sometimes called bolides. They are not really 
round in shape, although they often look so while 
traversing the sky, but their forms are fragmentary, 
and occasionally fantastic. It has been supposed 
that their origin is different from that of the true 
meteors; it has even been conjectured that they may 
have originated from the giant volcanoes of the moon 
or have been shot out from the sun during some of the 
tremendous explosions that accompany the formation 
of eruptive prominences. By the same reasoning 
some of them might be supposed to have come from 
some distant star. Others have conjectured that they 
are wanderers in space, of unknown origin, which the 
earth encounters as it journeys on, and Lord Kelvin 

195 



CURIOSITIES OF THE SKY 

made a suggestion which has become classic because 
of its imaginative reach — viz., that the first germs of 
life may have been brought to the earth by one of 
these bodies, ''a fragment of an exploded world." 

It is a singular fact that astronomers and scien- 
tific men in general were among the last to admit 
the possibility of solid masses falling from the sky. 
The people had believed in the reality of such phenom- 
ena from the earliest times, but the savants shook 
their heads and talked of superstition. This was the 
less surprising because no scientifically authenticated 
instance of such an occurrence was known, and the 
stones popularly believed to have fallen from the sky 
had become the objects of worship or superstitious 
reverence, a fact not calculated to recommend them 
to scientific credence. The celebrated "black stone" 
suspended in the Kaaba at Mecca is one of these 
reputed gifts from heaven ; the * ' Palladium " of ancient 
Troy was another; and a stone which fell near En- 
sisheim, in Germany, was placed in a church as an 
object to be religiously venerated. Many legends of 
falling stones existed in antiquity, some of them curi- 
ously transfigured by the imagination, like the "Lion 
of the Peloponnesus," which was said to have sprung 
down from the sky upon the Isthmus of Corinth. But 
near the beginning of the nineteenth century, in 1803, 
a veritable shower of falling stones occurred at L*Aigle, 
in Northern France, and this time astronomers took 
note of the phenomenon and scientifically investigated 
it. Thousands of the strange projectiles came from 
the sky on this occasion, and were scattered over a 
wide area of country, and some buildings were hit. 

196 



METEORS, FIRE-BALLS, METEORITES 

Four years later another shower of stones occurred at 
Weston, Conn,, numbering thousands of individuals. 
The local alarm created in both cases was great, as 
well it might be, for what could be more intimidating 
than to find the blue vault of heaven suddenly hurling 
solid missiles at the homes of men? After these 
occurrences it was impossible for the most skeptical 
to doubt any longer, and the regular study of "aero- 
lites," or "meteorites," began. 

One of the first things recognized was the fact that 
fire-balls are solid meteorites in flight, and not gaseous 
exhalations in the air, as some had assumed. They 
bum in the air during their flight, and sometimes, per- 
haps, are entirely consumed before reaching the 
ground. Their velocity before entering the earth's 
atmosphere is equal to that of the planets in their 
orbits — viz., from twenty to thirty miles per second — 
a fact which proves that the sun is the seat of the 
central force governing them. Their burning in the 
air is not difficult to explain; it is the heat of friction 
which so quickly brings them to incandescence. Cal- 
culation shows that a body moving through the air 
at a velocity of about a mile per second will be brought, 
superficially, to the temperature of "red heat" by 
friction with the atmosphere. If its velocity is twenty 
miles per second the temperature will become thou- 
sands of degrees. This is the state of affairs with a 
meteorite rushing into the earth's atmosphere; its 
surface is liquefied within a few seconds after the 
friction begins to act, and the melted and vaporized 
portion of its mass is swept backward, forming the 
train of sparks that follows every great fire-ball. How- 

197 



CURIOSITIES OF THE SKY 

ever, there is one phenomenon connected with the 
trains of meteorites which has never been satisfac- 
torily explained: they often persist for long periods 
of time, drifting and turning with the wind, but not 
ceasing to glow with a phosphorescent luminosity. 
The question is, Whence comes this light? It must 
be light without heat, since the fine dust or vapor 
of which the train can only consist would not retain 
sufficient heat to render it luminous for so long a time. 
An extremely remarkable incident of this kind oc- 
curred on February 22, 1909, when an immense fire- 
ball that passed over southern England left a train 
that remained visible during two hours, assuming 
many curious shapes as it was drifted about by cur- 
rents in the air. 

But notwithstanding the enormous velocity with 
which meteorites enter the air they are soon slowed 
down to comparatively moderate speed, so that when 
they disappear they are usually travelling not faster 
than a mile a second. The courses of many have been 
traced by observers situated along their track at 
various points, and thus a knowledge has been ob- 
tained of their height above the grotmd during their 
flight and of the length of their visible courses. They 
generally appear at an elevation of eighty or a hun- 
dred miles, and are seldom visible after having de- 
scended to within five miles of the ground, unless the 
observer happens to be near the striking-point, when 
he may actually witness the fall. Frequently they 
burst while high in the air and their fragments are 
scattered like shrapnel over the surface of the ground, 
sometimes covering an area of several square miles, 

198 




A METEOR PHOTOGRAPHED IN FLIGHT 



METEORS, FIRE-BALLS, METEORITES 

but of course not thickly; different fragments of the 
same meteorite may reach the ground at points several 
miles apart. The observed length of their courses in 
the atmosphere varies from fifty to five hundred 
miles. If they continued a long time in flight after 
entering the air, even the largest of them would prob- 
ably be consumed to the last scrap, but their fiery 
career is so short on account of their great speed that 
the heat does not have time to penetrate very deeply, 
and some that have been picked up immediately after 
their fall have been found cold as ice within. Their 
size after reaching the ground is variable within wide 
limits ; some are known which weigh several tons, but 
the great majority weigh only a few pounds and many 
only a few ounces. 

Meteorites are of two kinds: stony meteorites and 
iron meteorites. The former outnumber the latter 
twenty to one; but many stone meteorites contain 
grains of iron. Nickel is commonly found in iron 
meteorites, so that it might be said that that redoubt- 
able alloy nickel-steel is of cosmical invention. Some 
twenty-five chemical elements have been found in 
meteorites, including carbon and the ** sun-metal, " 
helium. The presence of the latter is certainly high- 
ly suggestive in connection with the question of the 
origin of meteorites. The iron meteorites, besides 
metallic iron and nickel, of which they are almost en- 
tirely composed, contain hydrogen, helium, and car- 
bonic oxide, and about the only imaginable way in 
which these gases could have become absorbed in the 
iron would be through the immersion of the latter 
while in a molten or vaporized state in a hot and 

20I 



CURIOSITIES OF THE SKY 

dense atmosphere composed of them, . a condition 
which we know to exist only in the envelopes of the 
sun and the stars. 

The existence of carbon in the Canyon Diablo iron 
meteorites is attended by a circumstance of the most 
singular character — a very "fairy tale of science." 
In some cases the carbon has become diamond! These 
meteoric diamonds are very small ; nevertheless, they 
are true diamonds, resembling in many ways the little 
black gems produced by Moissan's method with the 
aid of the electric furnace. The fact that they are 
found embedded in these iron meteorites is another 
argument in favor of the hypothesis of the solar or 
stellar origin of the latter. To appreciate this it is 
necessary to recall the way in which Moissan made his 
diamonds. It was by a combination of the effects of 
great heat, great pressure, and sudden or rapid super- 
ficial cooling on a mass of iron containing carbon. 
When he finally broke open his iron he found it a 
pudding stuffed with miniature black diamonds. 
When a fragment of the Canyon Diablo meteoric iron 
was polished in Philadelphia over fifteen years ago it 
cut the emery-wheel to pieces, and examination 
showed that the damage had been effected by micro- 
scopic diamonds peppered through the mass. How 
were those diamonds formed? If the sun or Sirius 
was the laboratory that prepared them, we can get a 
glimpse at the process of their formation. There is 
plenty of heat, plenty of pressure, and an abundance 
of vaporized iron in the sun and the stars. When a 
great solar eruption takes place, masses of iron which 
have absorbed carbon may be shot out with a velocity 

202 



METEORS, FIRE-BALLS, METEORITES 

which forbids their return. Plunged into the fright- 
ful cold of space, their surfaces are quickly cooled, as 
Moissan cooled his prepared iron by throwing it into 
water, and thus the requisite stress is set up within, 
and, as the iron solidifies, the included carbon crys- 
tallizes into diamonds. Whether this explanation has 
a germ of truth in it or not, at any rate it is evident 
that iron meteorites were not created in the form in 
which they come to us; they must once have been 
parts of immeasurably more massive bodies than 
themselves. 

The fall of meteorites offers an appreciable, though 
numerically insignificant, peril to the inhabitants of 
the earth. Historical records show perhaps three or 
four instances of people being killed by these bodies. 
But for the protection afforded by the atmosphere, 
which acts as a very effective shield, the danger 
would doubtless be very much greater. In the 
absence of an atmosphere not only would more 
meteorites reach the ground, but their striking force 
would be incomparably greater, since, as we have 
seen, the larger part of their original velocity is de- 
stroyed by the resistance of the air. A meteorite 
weighing many tons and striking the earth with a 
velocity of twenty or thirty miles per second, would 
probably cause frightful havoc. 

It is a singular fact that recent investigations 
seem to have proved that an event of this kind actu- 
ally happened in North America — perhaps not long^er 
than a thousand or two thousand years ago. The 
scene of the supposed catastrophe is in northern 
central Arizona, at Coon Butte, where there is a 

203 



CURIOSITIES OF THE SKY 

nearly circular crater in the middle of a circular 
elevation or small mountain. The crater is some- 
what over four thousand feet in diameter, and the 
surrounding rim, formed of upturned strata and 
ejected rock fragments, rises at its highest point 
one hundred and sixty feet above the plain. The 
crater is about six hundred feet in depth — that is, from 
the rim to the visible floor or bottom of the crater. 
There is no evidence that volcanic action has ever 
taken place in the immediate neighborhood of Coon 
Butte. The rock in which the crater has been made 
is composed of horizontal sandstone and limestone 
strata. Between three hundred and four hundred 
million tons of rock fragments have been detached, 
and a large portion hurled by some cause out of the 
crater. These fragments lie concentrically distribut- 
ed around the crater, and in large measure form the 
elevation known as Coon Butte. The region has been 
famous for nearly twenty years on account of the 
masses of meteoric iron found scattered about and 
known as the "Canyon Diablo" meteorites. It was 
one of these masses, which consist of nickel-iron con- 
taining a small quantity of platinum, and of which 
in all some ten tons have been recovered for sale to 
the various collectors throughout the world, that as 
before mentioned destroyed the grinding - tool at 
Philadelphia through the cutting power of its em- 
bedded diamonds. These meteoric irons are scattered 
about the crater-hill, in concentric distribution, to a 
maximum distance of about five miles. When the 
suggestion was first made in 1896 that a monster 
meteorite might have created by its fall this singular 

204 



METEORS, FIRE-BALLS, METEORITES 

lone crater in stratified rocks, it was greeted with in- 
credulous smiles; but since then the matter has as- 
sumed a different aspect. The Standard Iron Com- 
pany, formed by Messrs. D. M. Barringer, B. C. 
Tilghman, E. J. Bennitt, and S. J. Holsinger, having 
become, in 1903, the owner of this freak of nature, 
sunk shafts and bored holes to a great depth in the 
interior of the crater, and also trenched the slopes of 
the mountain, and the result of their investigations 
has proved that the meteoric hypothesis of origin is 
correct. (See the papers published in the Proceedings 
of the Academy of Natural Sciences of Philadelphia, 
December, 1905, wherein it is proved that the United 
States Geological Survey was wrong in believing this 
crater to have been due to a steam explosion. Since 
that date there has been discovered a great amount 
of additional confirmatory proof.) Material of unmis- 
takably meteoric origin was found by means of the 
drills, mixed with crushed rock, to a depth of six 
hundred to seven hundred feet below the floor of the 
crater, and a great deal of it has been found admixed 
with the ejected rock fragments on the outer slopes 
of the mountain, absolutely proving synchronism be- 
tween the two events, the formation of this great 
crater and the falling of the meteoric iron out of the 
sky. The drill located in the bottom of the crater 
was sent, in a number of cases, much deeper (over one 
thousand feet) into unaltered horizontal red sand- 
stone strata, but no meteoric material was found 
below this depth (seven hundred feet, or between 
eleven and twelve hundred feet below the level of the 
surrounding plain), which has been assumed as being 
XI 207 



CURIOSITIES OF THE SKY 

about the limit of penetration. It is not possible 
to sink a shaft at present, owing to the water which 
has drained into the crater, and which forms, with 
the finely pulverized sandstone, a very troublesome 
quicksand encountered at about two hundred feet 
below the visible floor of the crater. As soon as this 
water is removed by pumping it will be easy to explore 
the depths of the crater by means of shafts and drifts. 
The rock strata (sandstone and limestone) of which 
the walls consist present every appearance of having 
been violently upturned by a huge body penetrating 
the earth like a cannon-ball. The general aspect of 
the crater strikingly resembles the impression made 
by a steel projectile shot into an armor-plate. Mr. 
Tilghman has estimated that a meteorite about five 
hundred feet in diameter and moving with a velocity 
of about five miles per second would have made just 
such a perforation upon striking rocks of the character 
of those found at this place. There was some fusion 
of the colliding masses, and the heat produced some 
steam from the small amount of water in the rocks. 
As a result there has been found at depth a consider- 
able amount of fused quartz (original sandstone) , and 
with it innumerable particles or sparks of fused 
nickel-iron (original meteorite). A projectile of that 
size penetrating eleven to twelve hundred feet into 
the rocky shell of the globe must have produced a 
shock which was perceptible several hundred miles 
away. 

The great velocity ascribed to the supposed mete- 
orite at the moment of striking could be accounted 
for by the fact that it probably plunged nearly 

208 



METEORS, FIRE-BALLS, METEORITES 

vertically downward, for it formed a circular crater 
in the rocky crust of the earth. In that case it 
would have been less retarded by the resistance 
of the atmosphere than are meteorites which enter the 
air at a lower angle and shoot ahead hundreds of 
miles until friction has nearly destroyed their original 
motion when they drop upon the earth. Some 
meteoric masses of great size, such as Peary's iron 
meteorite found at Cape York, Greenland, and the 
almost equally large mass discovered at Bacubirito, 
Mexico, appear to have penetrated but slightly on 
striking the earth. This may be explained by sup- 
posing that they pursued a long, horizontal course 
through the air before falling. The result would be 
that, their original velocity having been practically de- 
stroyed, they would drop to the ground with a velocity 
nearly corresponding to that which gravity would 
impart within the perpendicular distance of their 
final fall. A six-hundred-and-sixty-pound meteorite, 
which fell at Knyahinya, Hungary, striking at an 
angel of 27° from the vertical, penetrated the ground 
to a depth of eleven feet. 

It has been remarked that the Coon Butte meteor- 
ite may have fallen not longer ago than a few thou- 
sand years. This is based upon the fact that the 
geological indications favor the supposition that the 
event did not occur more than five thousand years 
ago, while on the other hand the rings of growth 
in the cedar-trees growing on the slopes of the crater 
show that they have existed there about seven hun- 
dred years. Prof. William H. Pickering has recently 
correlated this with an ancient chronicle which states 

211 



CURIOSITIES OF THE SKY 

that at Cairo, Egypt, in the year 1029, "many stars 
passed with a great noise." He remarks that Cairo 
is about 100°, by great circle, from Coon Butte, so 
that if the meteorite that made the crater was a 
member of a flock of similar bodies which encountered 
the earth moving in parallel lines, some of them might 
have traversed the sky tangent to the earth's surface 
at Cairo. That the spectacle spoken of in the chron- 
icle was caused by meteorites he deems exceedingly 
probable because of what is said about "a great noise " ; 
meteorites are the only celestial phenomena attended 
with perceptible sounds. Professor Pickering con- 
jectures that this supposed flock of great meteorites 
may have formed the nucleus of a comet which struck 
the earth, and he finds confirmation of the idea in the 
fact that out of the ten largest meteorites known, no 
less than seven were found within nine hundred miles 
of Coon Butte. It would be interesting if we could 
trace back the history of that comet, and find out what 
malicious planet caught it up in its innocent wan- 
derings and hurled it with so true an aim at the earth ! 
This remarkable crater is one of the most interesting 
places in the world, for there is absolutely no record 
of such a mass, possibly an iron-headed comet, from 
outer space having come into collision with our earth. 
The results of the future exploration of the depths of 
the crater will be awaited with much interest. 




■'<^^-''>^^r^:^m'^^!AiiE^lf^'ifisii^S^M ^ !;■,, ^iai^^-va| 



WESTERN PART OF THE MARE SERENITATIS 



XII 

THE WRECKING OF THE MOON 

THERE are sympathetic moods under whose in- 
fluence one gazes with a certain poignant ten- 
derness at the worn face of the moon; that little 
''fossil world" (the child of our mother earth, too) 
bears such terrible scars of its brief convulsive lifie 
that a sense of pity is awakened by the sight. The 
moon is the wonder-land of the telescope. Those 
towering mountains, whose ''proud aspiring peaks" 
cast silhouettes of shadow that seem drawn with india- 
ink ; those vast plains, enchained with gentle winding 
hills and bordered with giant ranges; those oval 
"oceans," where one looks expectant for the flash of 
wind- whipped waves; those enchanting "bays" and 
recesses at the seaward feet of the Alps; those broad 
straits passing between guardian heights incom- 
parably mightier than Gibraltar; those locket-like 
valleys as secluded among their mountains as the 
Vale of Cashmere; those colossal craters that make 
us smile at the pretensions of Vesuvius, Etna, and 
Cotopaxi; those strange white ways which pass with 
the unconcern of Roman roads across mountain, gorge, 
and valley — all these give the beholder an irresistible 
impression that it is truly a world into which he is 

213 



CURIOSITIES OF THE SKY 

looking, a world akin to ours, and yet no more like 
our world than Pompeii is like Naples. Its air, its 
waters, its clouds, its life are gone, and only a skeleton 
remains — a mute but eloquent witness to a cosmical 
tragedy without parallel in the range of human 
knowledge. 

One cannot but regret that the moon, if it ever was 
the seat of intelligent life, has not remained so until 
our time. Think what the consequences would have 
been if this other world at our very door had been 
found to be both habitable and inhabited! We talk 
rather airily of communicating with Mars by signals; 
but Mars never approaches nearer than 35,000,000 
miles, while the moon when nearest is only a little more 
than 2 20,000 miles away. Given an effective magnify- 
ing power of five thousand diameters, which will per- 
haps be possible at the mountain observatories as 
telescopes improve, and we should be able to bring 
the moon within an apparent distance of about forty 
miles, while the corresponding distance for Mars would 
be more than seven thousand miles. But even with 
existing telescopic powers we can see details on the 
moon no larger than some artificial constructions on 
the earth. St. Peter's at Rome, with the Vatican 
palace and the great piazza, if existing on the moon, 
would unquestionably be recognizable as something 
else than a freak of nature. Large cities, with their 
radiating lines of communication, v/ould at once be- 
tray their real character. Cultivated tracts, and the 
changes produced by the interference of intelligent 
beings, would be clearly recognizable. The electric 
illumination of a large town at night would probably 

214 



THE WRECKING OF THE MOON 

be markedly visible. Gleams of reflected sunlight 
would come to us from the surfaces of the lakes and 
oceans, and a huge "liner" traversing a lunar sea 
could probably be followed by its trail of smoke. As 
to communications by "wireless" signals, which cer- 
tain enthusiasts have thought of in connection with 
Mars, in the case of the moon they should be a rela- 
tively simple matter, and the feat might actually be 
accomplished. Think what a literature would grow 
up about the moon if it were a living world ! Its very 
differences from the earth would only accentuate its 
interest for us. Night and day on the moon are each 
two weeks in length; how interesting it would be to 
watch the manner in which the lunarians dealt with 
such a situation as that. Lunar and terrestrial history 
would keep step with each other, and we should record 
them both. Truly one might well wish to have a 
neighbor world to study ; one would feel so much the 
less alone in space. 

It is not impossible that the moon did at one time 
have inhabitants of some kind. But, if so, they van- 
ished with the disappearance of its atmosphere and 
seas, or with the advent of its cataclysmic age. At the 
best, its career as a living world must have been brief. 
If the water and air were gradually absorbed, as some 
have conjectured, by its cooling interior rocks, its sur- 
face might, nevertheless, have retained them for long 
ages; but if, as others think, their disappearance was 
due to the escape of their gaseous molecules in con- 
sequence of the inability of the relatively small lunar 
gravitation to retain them, then the final catastrophe 
must have been as swift as it was inevitable. Ac- 

215 



CURIOSITIES OF THE SKY 

cepting Darwin's hypothesis, that the moon was 
separated from the earth by tidal action while both 
were yet plastic or nebulous, we may reasonably con- 
clude that it began its career with a good supply of 
both water and air, but did not possess sufficient 
mass to hold them permanently. Yet it may have 
retained them long enough for life to develop in 
many forms upon its surface; in fact, there are so 
many indications that air and water have not always 
been lacking to the lunar world that we are driven 
to invent theories to explain both their former presence 
and their present absence. 

But whatever the former condition of the moon 
may have been, its existing appearance gives it a 
resistless fascination, and it bears so clearly the story 
of a vast catastrophe sculptured on its rocky face that 
the thoughtful observer cannot look upon it without 
a feeling of awe. The gigantic character of the lunar 
features impresses the beholder not less than the uni- 
versality of the play of destructive forces which they 
attest. Let us make a few comparisons. Take the 
lunar crater called "Tycho," which is a typical ex- 
ample of its kind. In the telescope Tycho appears as a 
perfect ring surrounding a circular depression, in the 
centre of which rises a group of mountains. Its 
superficial resemblance to some terrestrial volcanic 
craters is very striking. Vesuvius, seen from a point 
vertically above, would no doubt look something like 
that (the resemblance would have been greater when 
the Monte del Cavallo formed a more complete circuit 
about the crater cone) . But compare the dimensions. 
The remains of the outer crater ring of Vesuvius are 

216 




THE CRATERS CLAVIUS, LONGOMONTANUS, TYCHO, ETC. 



THE WRECKING OF THE MOON 

perhaps half a mile in diameter, while the active crater 
itself is only two or three hundred feet across at the 
most ; Tycho has a diameter of fifty- four miles ! The 
group of relatively insignificant peaks in the centre of 
the crater floor of Tycho is far more massive than the 
entire mountain that we call Vesuvius. The largest 
known volcanic crater on the earth, Aso San, in Japan, 
has a diameter of seven miles; it would take sixty 
craters like Aso San to equal Tycho in area! And 
Tycho, though one of the most perfect, is by no means 
the largest crater on the moon. Another, called 
"Theophilus," has a diameter of sixty- four miles, and 
is eighteen thousand feet deep. There are hundreds 
from ten to forty miles in diameter, and thousands 
from one to ten miles. They are so numerous in 
many places that they break into one another, like the 
cells of a crushed honeycomb. 

The lunar craters differ from those of the earth more 
fundamentally than in the matter of mere size; they 
are not situated on the tops of mountains. If they were, 
and if all the proportions were the same, a crater like 
Tycho might crown a conical peak fifty or one hundred 
miles high ! Instead of being cavities in the summits 
of mountains, the lunar craters are rather gigantic sink- 
holes whose bottoms in many cases lie two or three 
miles below the general surface of the lunar world. 
Around their rims the rocks are piled up to a height 
of from a few hundred to two or three thousand feet, 
with a comparatively gentle inclination, but on the 
inner side they fall away in gigantic broken precipices 
which make the dizzy cliffs of the Matterhorn seem 
but ''lover's leaps." Down they drop, ridge below 

219 



CURIOSITIES OF THE SKY 

ridge crag under crag, tottering wall beneath wall, un- 
til, in a crater named " Newton," near the south lunar 
pole, they attain a depth where the rays of the sun 
never reach. Nothing more frightful than the spec- 
tacle which many of these terrible chasms present can 
be pictured by the imagination. As the lazy lunar 
day slowly advances, the sunshine, unmitigated by 
clouds or atmospheric veil of any kind, creeps across 
their rims and begins to descend the opposite walls. 
Presently it strikes the ragged crest of a ridge which 
had lain hidden in such darkness as we never know 
on the earth, and runs along it like a line of kindling 
fire. Rocky pinnacles and needles shoot up into the 
sunlight out of the black depths. Down sinks the 
line of light, mile after mile, and continually new 
precipices and cliffs are brought into view, until at 
last the vast floor is attained and begins to be illumi- 
nated. In the mean while the sun's rays, darting 
across the gulf, have touched the summits of the 
central peaks, twenty or thirty miles from the crater's 
inmost edge, and they immediately kindle and blaze 
like huge stars amid the darkness. So profound are 
some of these awful craters that days pass before the 
sun has risen high enough above them to chase the 
last shadows from their depths. 

Although several long ranges of mountains resem- 
bling those of the earth exist on the moon, the great 
majority of its elevations assume the crateriform as- 
pect. Sometimes, instead of a crater, we find an 
immense mountain ring whose form and aspect hard- 
ly suggest volcanic action. But everywhere the true 
craters are in evidence, even on the sea-beds, al- 

220 



THE WRECKING OF THE MOON 

though they attain their greatest number and size 
on those parts of the moon — covering sixty per cent. 
of its visible surface — ^which are distinctly mountain- 
ous in character and which constitute its most brill- 
iant portions. Broadly speaking, the southwestern 
half of the moon is the most mountainous and broken, 
and the northeastern half the least so. Right down 
through the centre, from pole to pole, runs a wonder- 
ful line of craters and crateriform valleys of a magni- 
tude stupendous even for the moon. Another similar 
line follows the western edge. Three or four ''seas" 
are thrust between these mountainous belts. By the 
effects of ''libration" parts of the opposite hemi- 
sphere of the moon which is turned away from the 
earth are from time to time brought into view, and 
their aspect indicates that that hemisphere resembles 
in its surface features the one which faces the earth. 
There are many things about the craters which seem 
to give some warrant for the hypothesis which has 
been particularly urged by Mr. W. K. Gilbert, that 
they were formed by the impact of meteors; but 
there are also many things which militate against 
that idea, and, upon the whole, the volcanic theory 
of their origin is to be preferred. 

The enormous size of the lunar volcanoes is not so 
difficult to account for when we remember how slight 
is the force of lunar gravity as compared with that of 
the earth. With equal size and density, bodies on 
the moon weigh only one-sixth as much as on the 
earth. Impelled by the same force, a projectile that 
would go ten miles on the earth would go sixty miles 
on the moon. A lunar giant thirty-five feet tall 

221 



CURIOSITIES OF THE SKY 

would weigh no more than an ordinary son of Adam 
weighs on his greater planet. To shoot a body from 
the earth so that it would not drop back again, we 
should have to start it with a velocity of seven miles 
per second; a mile and a half per second would serve 
on the moon. It is by no means difficult to believe, 
then, that a lunar volcano might form a crater ring 
eight or ten times broader than the greatest to be 
found on the earth, especially when we reflect that 
in addition to the relatively slight force of gravity, 
the materials of the lunar crust are probably lighter 
than those of our terrestrial rocks. 

For similar reasons it seems not impossible that 
the theory mentioned in a former chapter — ^that 
some of the meteorites that have fallen upon the 
earth originated from the lunar volcanoes— is well 
founded. This would apply especially to the stony 
meteorites, for it is hardly to be supposed that the 
moon, at least in its superficial parts, contains much 
iron. It is surely a scene most strange that is thus 
presented to the mind's eye — that little attendant 
of the earth's (the moon has only one-fiftieth of the 
volume, and only one-eightieth of the mass of the 
Hearth) firing great stones back at its parent planet! 
And what can have been the cause of this furious 
outbreak of volcanic forces on the moon ? Evidently 
it was but a passing stage in its history; it had en- 
joyed more quiet times before. As it cooled down 
from the plastic state in which it parted from the 
earth, it became incrusted after the normal manner 
of a planet, and then oceans were formed, its atmos- 
phere being sufficiently dense to prevent the water 

222 



THE WRECKING OF THE MOON 

from evaporating and the would-be oceans from dis- 
appearing continually in mist. This, if any, must 
have been the period of life in the lunar world. As 
we look upon the vestiges of that ancient world buried 
in the wreck that now covers so much of its surface, 
it is difficult to restrain the imagination from pictur- 
ing the scenes which were once presented there; and, 
in such a case, should the imagination be fettered? 
We give it free rein in terrestrial life, and it rewards 
us with some of our greatest intellectual pleasures. 
The wonderful landscapes of the moon offer it an 
ideal field with just enough half-hidden suggestions 
of facts to stimulate its powers. 

The great plains of the Mare Imhrium and the Mare 
Serenitatis (the "Sea of Showers" and the "Sea of 
Serenity"), bordered in part by lofty mountain 
ranges precisely like terrestrial mountains, scalloped 
along their shores with beautiful bays curving back 
into the adjoining highlands, and united by a great 
strait passing between the nearly abutting ends of 
the "Lunar Apennines" and the "Lunar Caucasus," 
offer the elements of a scene of world beauty such as 
it would be difficult to match upon our planet. Look 
at the finely modulated bottom of the ancient sea in 
Mr. Ritchey's exquisite photograph of the western 
part of the Mare Serenitatis, where one seems to see 
the play of the watery currents heaping the ocean 
sands in waving lines, making shallows, bars, and 
deeps for the mariner to avoid or seek, and affording 
a playground for the creatures of the main. What 
geologist would not wish to try his hammer on those 
rocks with their stony pages of fossilized history? 

225 



CURIOSITIES OF THE SKY 

There is in us an instinct which forbids us to think 
that there was never any life there. If we could 
visit the moon, there is not among us a person so 
prosaic and unimaginative that he would not, the 
very first thing, begin to search for traces of its in- 
habitants. We would look for them in the deposits 
on the sea bottoms; we would examine the shores 
wherever the configuration seemed favorable for har- 
bors and the sites of maritime cities — forgetting that 
it may be a little ridiculous to ascribe to the ancient 
lunarians the same ideas that have governed the de- 
velopment of our race; we would search through the 
valleys and along the seeming courses of vanished 
streams; we would explore the mountains, not the 
terrible craters, but the pinnacled chains that recall 
our own Alps and Rockies ; seeking everywhere some 
vestige of the transforming presence of intelligent 
life. Perhaps we should find such traces, and per- 
haps, with all our searching, we should find nothing 
to suggest that life had ever existed amid that uni- 
versal ruin. 

Look again at the border of the *'Sea of Serenity" 
— ^what a name for such a scene! — and observe how 
it has been rent with almost inconceivable violence, 
the wall of the colossal crater Posidonius dropping 
vertically upon the ancient shore and obliterating it, 
while its giant neighbor, Le Monnier, opens a yawn- 
ing mouth as if to swallow the sea itself. A scene 
like this makes one question whether, after all, those 
may not be right who have imagined that the so-called 
sea bottoms are really vast plains of frozen lava 
which gushed up in floods so extensive that even 

226 




MARE TRANQUTLITATIS AND SURROUNDINGS 



THE WRECKING OF THE MOON 

the mighty volcanoes were half drowned in the fiery 
sea. This suggestion becomes even stronger when 
we turn to another of the photographs of Mr. Ritchey 's 
wonderful series, showing a part of the Mare Tran- 
quilitatis ("Sea of Tranquility"!). Notice how near 
the centre of the picture the outline of a huge ring 
with radiating ridges shows through the sea bottom; 
a fossil volcano submerged in a petrified ocean! 
This is by no means the only instance in which a 
buried world shows itself under the great lunar plains. 
Yet, as the newer craters in the sea itself prove, the 
volcanic activity survived this other catastrophe, or 
broke out again subsequently, bringing more ruin to 
pile upon ruin. 

Yet notwithstanding the evidence which we have 
just been considering in support of the hypothesis 
that the "seas" are lava floods, Messrs. Loewy and 
Puiseux, the selenographers of the Paris Observatory, 
are convinced that these great plains bear character- 
istic marks of the former presence of immense bodies 
of water. In that case we should be forced to con- 
clude that the later oceans of the moon lay upon vast 
sheets of solidified lava; and thus the catastrophe of 
the lunar world assumes a double aspect, the earliest 
oceans being swallowed up in molten floods issuing 
from the interior, while the lands were reduced to 
chaos by a universal eruption of tremendous vol- 
canoes ; and then a period of comparative quiet fol- 
lowed, during which new seas were formed, and new 
life perhaps began to flourish in the lunar world, only 
to end in another cataclysm, which finally put a term 
to the existence of the moon as a life-supporting world. 

229 



CURIOSITIES OF THE SKY 

Suppose we examine two more of Mr. Ritchey's 
illuminating photographs, and, first, the one showing 
the crater Theophilus and its surroundings. We have 
spoken of Theophilus before, citing the facts that it is 
sixty-four miles in diameter and eighteen thousand feet 
deep. It will be noticed that it has two brother 
giants — Cyrillus the nearer, and Catharina the more 
distant; but Theophilus is plainly the youngest of 
the trio. Centuries, and perhaps thousands of years, 
must have elapsed between the periods of their up- 
heaval, for the two older craters are partly filled 
with debris, while it is manifest at a glance that 
when the southeastern wall of Theophilus was formed, 
it broke away and destroyed a part of the more 
ancient ring of Cyrillus. There is no more tremendous 
scene on the moon than this ; viewed with a powerful 
telescope, it is absolutely appalling. 

The next photograph shows, if possible, a still 
wilder region. It is the part of the moon lying be- 
tween Tycho and the south pole. Tycho is seen in 
the lower left-hand part of the picture. To the right, 
at the edge of the illuminated portion of the moon, 
are the crater-rings, Longomontanus and WilhelmL, 
the former being the larger. Between them are to 
be seen the ruins of two or three more ancient craters 
which, together with portions of the walls of Wilhelm 
I. and Longomontanus, have been honeycombed 
with smaller craters. The vast crateriform depression 
above the centre of the picture is Clavius, an un- 
rivalled wonder of lunar scenery, a hundred and 
forty-two miles in its greatest length, while its whole 
immense floor has sunk two miles below the general 

230 




LUNAR CRATER THEOPHILUS AND SURROUNDING REGION 



THE WRECKING OF THE MOON 

surface of the moon outside the ring. The monstrous 
shadow-filled cavity above Clavius toward the right 
is Blancanus, whose aspect here gives a good idea of 
the appearance of these chasms when only their rims 
are in the sunlight. But observe the indescribable 
savagery of the entire scene. It looks as though 
the spirit of destruction had gone mad in this spot. 
The mighty craters have broken forth one after an- 
other, each rending its predecessor; and when their 
work was finished, a minor but yet tremendous out- 
break occurred, and the face of the moon was gored 
and punctured with thousands of smaller craters. 
These relatively small craters (small, however, only in 
a lunar sense, for many of them would appear gigantic 
on the earth) recall once more the theory of meteoric 
impact. It does not seem impossible that some of 
them may have been formed by such an agency. 

One would not wish for our planet such a fate as 
that which has overtaken the moon, but we cannot 
be absolutely sure that something of the kind may 
not be in store for it. We really know nothing of 
the ultimate causes of volcanic activity, and some 
have suggested that the internal energies of the earth 
may be accumulating instead of dying out, and may 
never yet have exhibited their utmost destructive 
power. Perhaps the best assurance that we can find 
that the earth will escape the catastrophe that has 
overtaken its satellite is to be found in the relatively 
great force of its gravitation. The moon has been 
the victim of its weakness ; given equal forces, and the 
earth would be the better able to withstand them. 
It is significant, in connection with these considera- 

233 



CURIOSITIES OF THE SKY 

tions, that the little planet Mercury, which seems 
also to have parted with its air and water, shows to 
the telescope some indications that it is pitted with 
craters resembling those that have torn to pieces the 
face of the moon. 

Upon the whole, after studying the dreadful lunar 
landscapes, one cannot feel a very enthusiastic sym- 
pathy with those who are seeking indications of the 
continued existence of some kind of life on the moon; 
such a world is better without inhabitants. It has 
met its fate; let it go! Fortunately, it is not so near 
that it cannot hide its scars and appear beautiful — 
except when curiosity impels us to look with the 
penetrating eyes of the astronomer. 




MARE CRISIUM 



XIII 

THE GREAT MARS PROBLEM 

LET any thoughtful person who is acquainted with 
^the general facts of astronomy look up at the 
heavens some night when they appear in their great- 
est splendor, and ask himself what is the strong- 
est impression that they make upon his mind. He 
may not find it easy to frame an answer, but when he 
has succeeded it will probably be to the effect that 
the stars give him an impression of the universality 
of intelligence; they make him feel, as the sun and 
the moon cannot do, that his world is not alone ; that 
all this was not made simply to form a gorgeous 
canopy over the tents of men. If he is of a devout 
turn of mind, he thinks, as he gazes into those fathom- 
less deeps and among those bewildering hosts, of the 
infinite multitude of created beings that the Al- 
mighty has taken under his care. The narrow ideas 
of the old geocentric theology, which made the earth 
God's especial footstool, and man his only rational 
creature, fall away from him like a veil that had 
obscured his vision; they are impossible in the pres- 
ence of what he sees above. Thus the natural ten- 
dency, in the light of modern progress, is to regard 
the universe as everywhere filled with life. 

237 



CURIOSITIES OF THE SKY 

But science, which is responsible for this broaden- 
ing of men's thoughts concerning the universaHty of 
life, itself proceeds to set limits. Of spiritual exist- 
ences it pretends to know nothing, but as to physical 
beings, it declares that it can only entertain the sup- 
position of their existence where it finds evidence of 
an environment suited to their needs, and such en- 
vironment may not ever3rvvhere exist. Science, 
though repelled by the antiquated theological con- 
ception of the supreme isolation of man among created 
beings, regards with complacency the probability 
that there are regions in the universe where no organic 
life exists, stars which shine upon no inhabited 
worlds, and planets which nourish no animate creat- 
ures. The astronomical view of the universe is that 
it consists of matter in every stage of evolution: 
some nebulous and chaotic; some just condensing 
into stars (suns) of every magnitude and order; some 
shaped into finished solar bodies surrounded by de- 
pendent planets; some forming stars that perhaps 
have no planets, and will have none ; some constitut- 
ing suns that are already aging, and will soon lose 
their radiant energy and disappear; and some ag- 
gregated into masses that long ago became inert, 
cold, and ray less, and that can only be revivified by 
means about which we can form conjectures, but of 
which we actually know nothing. 

As with the stars, so with the planets, which are 
the satellites of stars. All investigations unite to 
tell us that the planets are not all in the same state 
of development. As some are large and some small, 
so some are, in an evolutionary sense, young, and 

?38 



THE GREAT MARS PROBLEM 

some old. As they depend upon the suns around 
which they revolve for their light, heat, and other 
forms of radiant energy, so their condition varies 
with their distance from those suns. Many may 
never arrive at a state suitable for the maintenance 
of life upon their surfaces; some which are not at 
present in such a state may attain it later; and the 
forms of life themselves may vary with the peculiar 
environment that different planets afford. Thus we 
see that we are not scientifically justified in affirming 
that life is ubiquitous, although we are thus justified 
in saying that it must be, in a general sense, universal. 
We might liken the universe to a garden known to 
contain every variety of plant. If on entering it we 
see no flowers, we examine the species before us and 
find that they are not of those which bloom at this 
particular season, or perhaps they are such as never 
bear flowers. Yet we feel no doubt that we shall find 
flowers somewhere in the garden, because there are 
species which bloom at this season, and the garden 
contains all varieties. 

While it is tacitly assumed that there are planets 
revolving around other stars than the sun, it would 
be impossible for us to see them with any telescope 
yet invented, and no instrument now in the 
posession of astronomers could assure us of their 
existence; so the only planetary system of which 
we have visual knowledge is our own. Excluding 
the asteroids, which could not from any point of 
view be considered as habitable, we have in the solar 
system eight planets of various sizes and situated at 
various distances from the sun. Of these eight we 

239 



CURIOSITIES OF THE SKY 

know that one, the earth, is inhabited. The ques- 
tion, then, arises : Are there any of the others which 
are inhabited or habitable ? Since it is our intention 
to discuss the habitabiHty of only one of the seven 
to which the question applies, the rest may be dis- 
missed in a few words. The smallest of them, and 
the nearest to the sun, is Mercury, which is regarded 
as uninhabitable because it has no perceptible supply 
of water and air, and because, owing to the extraor- 
dinary eccentricity of its orbit, it is subjected to 
excessive and very rapid alterations in the amount 
of solar heat and light poured upon its surface, such 
alterations being inconsistent with the supposition 
that it can support living beings. Even its average 
temperature is more than six and a half times that 
prevailing on the earth! Another circumstance 
which militates against its habitability is that, ac- 
cording to the results of the best telescopic studies, 
it always keeps the same face toward the sun, so that 
one half of the planet is perpetually exposed to the 
fierce solar rays, and the other half faces the un- 
mitigated cold of open space. Venus, the next in 
distance from the sun, is almost the exact twin of 
the earth in size, and many arguments may be urged 
in favor of its habitability, although it is suspected 
of possessing the same peculiarity as Mercury, in 
always keeping the same side sunward. Unfortu- 
nately its atmosphere appears to be so dense that 
no permanent markings on its surface are certainly 
visible, and the question of its actual condition must, 
for the present, be left in abeyance. Mars, the first 
planet more distant from the sun than the earth, is 

240 



THE GREAT MARS PROBLEM 

the special subject of this chapter, and will be de- 
scribed and discussed a few lines further on. Jupiter, 
Saturn, Uranus, and Neptune, the four giant planets, 
all more distant than Mars, and each more distant 
than the other in the order named, are all regarded 
as uninhabitable because none of them appears to 
possess any degree of solidity. They may have solid 
or liquid nuclei, but exteriorly they seem to be mere 
balls of cloud. Of course, one can imagine what he 
pleases about the existence of creatures suited to the 
physical constitution of such planets as these, but 
they must be excluded from the category of habitable 
worlds in the ordinary sense of the term. We go 
back, then, to Mars. 

It will be best to begin with a description of the 
planet. Mars is 4230 miles in diameter; its surface 
is not much more than one-quarter as extensive as 
that of the earth (.285). Its mean distance from the 
sun is 141,500,000 miles, 48,500,000 miles greater than 
that of the earth. Since radiant energy varies in- 
versely as the square of distance, Mars receives less 
than half as much solar light and heat as the earth 
gets. Mars' year (period of revolution round the 
sun) is 687 days. Its mean density is 71 per cent, 
of the earth's, and the force of gravity on its surface 
is 38 per cent, of that on the surface of the earth; 
i.e., a body weighing one hundred pounds on the 
earth would, if transported to Mars, weigh but thirty- 
eight pounds. The inclination of its equator to the 
plane of its orbit differs very little from that of the 
earth's equator, and its axial rotation occupies 24 
hours 37 minutes; so that the length of day and 

241 



CURIOSITIES OF THE SKY 

night, and the extent of the seasonal changes on 
Mars, are almost precisely the same as on the earth. 
But owing to the greater length of its year, the sea- 
sons of Mars, while occurring in the same order, are 
almost twice as long as ours. The surface of the 
planet is manifestly solid, like that of our globe, and 
the telescope reveals many permanent markings on 
it, recalling the appearance of a globe on which geo- 
graphical features have been represented in reddish 
and dusky tints. Around the poles are plainly to 
be seen rounded white areas, which vary in extent 
with the Martian seasons, nearly vanishing in sum- 
mer and extending widely in winter. The most 
recent spectroscopic determinations indicate that 
Mars has an atmosphere perhaps as dense as that to 
be found on our loftiest mountain peaks, and there 
is a perceptible amount of watery vapor in this 
atmosphere. The surface of the planet appears to 
be remarkably level, and it has no mountain ranges. 
No evidences of volcanic action have been discovered 
on Mars. The dusky and reddish areas were re- 
garded by the early observers as respectively seas 
and lands, but at present it is not believed that there 
are any bodies of water on the planet. There has 
never been much doubt expressed that the white 
areas about the poles represent snow. 

It will be seen from this brief description that many 
remarkable resemblances exist between Mars and the 
earth, and there is nothing wonderful in the fact that 
the question of the habitability of the former has be- 
come one of extreme and wide-spread interest, giving 
rise to the most diverse views, to many extraordinary 

242 



THE GREAT MARS PROBLEM 

speculations, and sometimes to regrettably heated 
controversy. The first champion of the habitability 
of Mars was Sir William Herschel, although even 
before his time the idea had been suggested. He 
was convinced by the revelations of his telescopes, 
continually increasing in power, that Mars was more 
like the earth than any other planet. He could not 
resist the testimony of the polar snows, whose sug- 
gestive conduct was in such striking accord with what 
occurs upon the earth. Gradually, as telescopes im- 
proved and observers increased in number, the prin- 
cipal features of the planet were disclosed and charted, 
and "areography," as the geography of Mars was 
called, took its place among the recognized branches 
of astronomical study. But it was not before 1877 
that a fundamentally new discovery in areography 
gave a truly sensational turn to speculation about 
life on "the red planet." In that year Mars made 
one of its nearest approaches to the earth, and was 
so situated in its orbit that it could be observed to 
great advantage from the northern hemisphere of 
the earth. The celebrated Italian astronomer, Schia- 
parelli, took advantage of this opportunity to make 
a trigonometrical survey of the surface of Mars — as 
coolly and confidently as if he were not taking his 
sights across a thirty-five-million-mile gulf of empty 
space — and in the course of this survey he was aston- 
ished to perceive that the reddish areas, then called 
continents, were crossed in many directions by narrow, 
dusky lines, to which he gave the suggestive name of 
"canals." Thus a kind of firebrand was cast into 
the field of astronomical speculation, which has ever 

343 



CURIOSITIES OF THE SKY 

since produced disputes that have sometimes ap- 
proached the violence of poHtical faction. At first 
the accuracy of SchiaparelH's observations was con- 
tested; it required a powerful telescope, and the 
most excellent "seeing," to render the enigmatical 
lines visible at all, and many searchers were unable to 
detect them. But Schiaparelli continued his studies 
in the serene sky of Italy, and produced charts of the 
gridironed face of Mars containing so much aston- 
ishing detail that one had either to reject them in 
ioto or to confess that Schiaparelli was right. As 
subsequent favorable oppositions of Mars occurred, 
other observers began to see the ''canals" and to 
confirm the substantial accuracy of the Italian as- 
tronomer's work, and finally few were found who 
would venture to affirm that the "canals" did not 
exist, whatever their meaning might be. 

When Schiaparelli began his observations it was 
generally believed, as we have said, that the dusky- 
areas on Mars were seas, and since Schiaparelli thought 
that the "canals" invariably began and ended at the 
shores of the "seas," the appropriateness of the title 
given to the lines seemed apparent. Their artificial 
character was immediately assumed by many, be- 
cause they were too straight and too suggestively 
geometrical in their arrangement to permit the con- 
clusion that they were natural watercourses. A 
most surprising circumstance noted by Schiaparelli 
was that the "canals" made their appearance after 
the melting of the polar snow in the corresponding 
hemisphere had begun, and that they grew darker, 
longer, and more numerous in proportion as the polar 

244 



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01 




THE GREAT MARS PROBLEM 

liquidation proceeded. Another very puzzling ob- 
servation was that many of them became double as 
the season advanced; close beside an already exist- 
ing ''canal," and in perfect parallelism with it, an- 
other would gradually make its appearance. That 
these phenomena actually existed and were not 
illusions was proved by later observations, and to- 
day they are seen whenever Mars is favorably situated 
for observation. 

In the closing decade of the nineteenth century, 
Mr. Percival Lowell took up the work where Schia- 
parelli had virtually dropped it, and soon added a 
great number of ''canals" to those previously known, 
so that in his charts the surface of the wonderful 
little planet appears covered as with a spider's web, 
the dusky lines criss-crossing in every direction, with 
conspicuous knots wherever a number of them come 
together. Mr. Lowell has demonstrated that the areas 
originally called seas, and thus named on the earlier 
charts, are not bodies of water, whatever else they 
may be. He has also found that the mysterious lines 
do not, as Schiaparelli supposed, begin and end at 
the edges of the dusky regions, but often continue 
on across them, reaching in some cases far up into 
the polar regions. But Schiaparelli was right in his 
observation that the appearance of the "canals" is 
synchronous with the gradual disappearance of the 
polar snows, and this fact has become the basis of 
the most extraordinary theory that the subject of 
life in other worlds has ever given birth to. 

Now, the effect of such discoveries, as we have 
related, depends upon the type of mind to whose 

247 



CURIOSITIES OP THE SKY 

attention they are called. Many are content to ac- 
cept them as strange and inexplicable at present, 
and to wait for further light upon them; others in- 
sist upon an immediate inquiry concerning their 
probable nature and meaning. Such an inquiry can 
only be based upon inference proceeding from analogy. 
Mars, say Mr. Lowell and those who are of his opin- 
ion, is manifestly a solidly incrusted planet like the 
earth; it has an atmosphere, though one of great 
rarity; it has water vapor, as the snows in them- 
selves prove ; it has the alternation of day and night, 
and a succession of seasons closely resembling those 
of the earth; its surface is suggestively divided into 
regions of contrasting colors and appearance, and 
upon that surface we see an immense number of lines 
geometrically arranged, with a system of symmetri- 
cal intersections where the lines expand into circular 
and oval areas — and all connected with the annual 
melting of the polar snows in a way which irresistibly 
suggests the interference of intelligence directed to 
a definite end. Why, with so many concurrent cir- 
cumstances to support the hypothesis, should we not 
regard Mars as an inhabited globe? 

But the differences between Mars and the earth are 
in many ways as striking as their resemblances. 
Mars is relatively small ; it gets less than half as much 
light and heat as we receive; its atmosphere is so 
rare that it would be distressing to us, even if we 
could survive in it at all; it has no lakes, rivers, or 
seas ; its surface is an endless prairie ; and its "canals " 
are phenomena utterly unlike anything on the earth. 
Yet it is precisely upon these divergences between 

248 



THE GREAT MARS PROBLEM 

the earth and Mars, this repudiation of terrestrial 
standards, that the theory of "hfe on Mars,*' for 
which Mr. Lowell is mainly responsible, is based. 
Because Mars is smaller than the earth, we are told 
it must necessarily be more advanced in planetary 
evolution, the underlying cause of which is the grad- 
ual cooling and contraction of the planet's mass. 
Mars has parted with its internal heat more rapidly 
than the earth; consequently its waters and its at- 
mosphere have been mostly withdrawn by chemical 
combinations, but enough of both yet remain to 
render life still possible on its surface. As the globe 
of Mars is evolutionally older than that of the earth, 
so its forms of organic life may be proportionally 
further advanced, and its inhabitants may have 
attained a degree of cultivated intelligence much 
superior to what at present exists upon the earth. 
Understanding the nature and the causes of the 
desiccation of their planet, and possessing engineer- 
ing science and capabilities far in advance of ours, 
they may be conceived to have grappled with the 
stupendous problem of keeping their world in a 
habitable condition as long as possible. Supposing 
them to have become accustomed to live in their 
rarefied atmosphere (a thing not inconceivable, since 
men can live for a time at least in air hardly less 
rare), the most pressing problem for them is that of 
a water-supply, without which plant life cannot exist, 
while animal life in turn depends for its existence 
upon vegetation. The only direction in which they 
can seek water is that of the polar regions, where it is 
alternately condensed into snow and released in the 

^49 



CURIOSITIES OF THE SKY 

liquid form by the effect of the seasonal changes. It 
is, then, to the annual melting of the polar snow-fields 
that the Martian engineers are supposed to have 
recourse in supplying the needs of their planet, and 
thus providing the means of prolonging their own 
existence. It is imagined that they have for this 
purpose constructed a stupendous system of irriga- 
tion extending over the temperate and equatorial 
regions of the planet. '^The ''canals" represent the 
lines of irrigation, but the narrow streaks that we see 
are not the canals themselves, but the irrigated bands 
covered by them. Their dark hue, and their gradual 
appearance after the polar melting has begun, are 
due to the growth of vegetation stimulated by the 
water. The rounded areas visible where several 
"canals" meet and cross are called by Mr. Lowell 
''oases." These are supposed to be the principal 
centres of population and industry. It must be con- 
fessed that some of them, with their complicated 
systems of radiating lines, appear to answer very well 
to such a theory. No attempt to explain them by 
analogy with natural phenomena on the earth has 
proved successful. 

But a great difficulty yet remains: How explain 
the seemingly miraculous powers of the supposed 
engineers? Here recourse is had once more to the 
relative smalkiess of the planet. We have remarked 
that the force of gravity on Mars is only thirty-eight 
per cent, of that on the earth. A steam -shovel 
driven by a certain horse-power would be nearly 
three times as effective there as here. A man of our 
stature on Mars would find his effective strength in- 

250 



THE GREAT MARS PROBLEM 

creased in the same proportion. But just because of 
the slight force of gravity there, a Martian might 
attain to the traditional stature of Goliath without 
finding his own weight an encumbrance to his activity, 
while at the same time his huge muscles would come 
into unimpeded play, enabling him single-handed to 
perform labors that would be impossible to a whole 
gang of terrestrial workmen. The effective powers 
of huge machines would be increased in the same 
way; and to all this must be added the fact that the 
mean density of the materials of which Mars is com- 
posed is much less than that of the constituents of 
the earth. Combining all these considerations, it 
becomes much less difficult to conceive that public 
works might be successfully undertaken on Mars 
which would be hopelessly beyond the limits of hu- 
man accomplishment. 

Certain other difficulties have also to be met; as, 
for instance, the relative coldness of the climate of 
Mars. At its distance it gets considerably less than 
half as much light and heat as we receive. In addi- 
tion to this, the rarity of its atmosphere would 
naturally be expected to decrease the effective tem- 
perature at the planet's surface, since an atmosphere 
acts somewhat like the glass cover of a hot-house in 
retaining the solar heat which has penetrated it. It 
has been calculated that, unless there are mitigating 
circumstances of which we know nothing, the aver- 
age temperature at the surface of Mars must be far 
below the freezing-point of water. To this it is re- 
plied that the possible mitigating circumstances 
spoken of evidently exist in fact, because we can see 

251 



CURIOSITIES OF THE SKY 

that the watery vapor condenses into snow around 
the poles in winter, but melts again when summer 
comes. The mitigating agent may be supposed to 
exist in the atmosphere where the presence of cer- 
tain gases would completely alter the temperature 
gradients. 

It might also be objected that it is inconceivable 
that the Martian engineers, however great may be 
their physical powers, and however gigantic the 
mechanical energies under their control, could force 
water in large quantities from the poles to the equator. 
This is an achievement that measures up to the cos- 
mical standard. It is admitted by the champions of 
the theory that the difficulty is a formidable one; 
but they call attention to the singular fact that on 
Mars there can be found no chains of mountains, and 
it is even doubtful if ranges of hills exist there. The 
entire surface of the planet appears to be almost 
**as smooth as a billiard ball," and even the broad 
regions which were once supposed to be seas apparent- 
ly lie at practically the same level as the other parts, 
since the "canals" in many cases run uninterrupted- 
ly across them. Lowell's idea is that these sombre 
areas may be expanses of vegetation covering ground 
of a more or less marshy character, for while the 
largest of them appear to be permanent, there are 
some which vary coincidently with the variations of 
the canals. 

As to the kind of machinery employed to force the 
water from the poles, it has been conjectured that it 
may have taken the form of a gigantic system of 
pumps and conduits; and since the Martians are 

252 



THE GREAT MARS PROBLEM 

assumed to be so far in advance of us in their mastery 
of scientific principles, the hypothesis will at least not 
be harmed by supposing that they have learned to 
harness forces of nature whose very existence in a 
manageable form is yet unrecognized on the earth. 
If we wish to let the imagination loose, we may con- 
jecture that they have conquered the secret of those 
intra-atomic forces whose resistless energy is begin- 
ning to become evident to us, but the possibility of 
whose utilization remains a dream, the fulfilment of 
which nobody dares to predict. 

Such, in very brief form, is the celebrated theory 
of Mars as an inhabited world. It certainly capti- 
vates the imagination, and if we believe it to repre- 
sent the facts, we cannot but watch with the deepest 
sympathy this gallant struggle of an intellectual race 
to preserve its planet from the effects of advancing 
age and death. We may, indeed, wonder whether 
our own humanity, confronted by such a calamity, 
could be counted on to meet the emergency with 
equal stoutness of heart and inexhaustibleness of 
resource. Up to the present time we certainly have 
shown no capacity to confront Nature toe to toe, and 
to seize her by the shoulders and turn her round 
when she refuses to go our way. If we could get into 
wireless telephonic communication with the Martians 
we might learn from their own lips the secret of their 

more than "Roman recovery.'* 
13 



XIV 

THE RIDDLE OF THE ASTEROIDS 

BETWEEN the orbits of Mars and Jupiter re- 
volves the most remarkable system of little 
bodies with which we are acquainted — the Asteroids, 
or Minor Planets. Some six hundred are now known, 
and they may actually number thousands. They 
form virtually a ring about the sun. The most strik- 
ing general fact about them is that they occupy the 
place in the sky which should be occupied, according 
to Bode's Law, by a single large planet. This fact, 
as we shall see, has led to the invention of one of the 
most extraordinary theories in astronomy — viz.y that 
of the explosion of a world ! 

Bode's Law, so-called, is only an empiric formula, 
but until the discovery of Neptune it accorded so 
well with the distances of the planets that astron- 
omers were disposed to look upon it as really repre- 
senting some underlying principle of planetary dis- 
tribution. They were puzzled by the absence of a 
planet in the space between Mars and Jupiter, where 
the *'law'* demanded that there should be one, and 
an association of astronomers was formed to search 
for it. There was a decided sensation when, in 1801, 
Piazzi, of Palermo, announced that he had found a 

254 



THE RIDDLE OF THE ASTEROIDS 

little planet which apparently occupied the place in 
the system which belonged to the missing body. 
He named it Ceres, and it was the first of the Asteroids. 
The next year Olbers, of Bremen, while looking for 
Ceres with his telescope, stumbled upon another small 
planet which he named Pallas. Immediately he was 
inspired with the idea that these two planets were 
fragments of a larger one which had formerly occu- 
pied the vacant place in the planetary ranks, and he 
predicted that others would be found by searching 
in the neighborhood of the intersection of the orbits 
of the two already discovered. This bold prediction 
was brilliantly fulfilled by the finding of two more — 
Juno in 1804, and Vesta in 1807. Olbers would seem 
to have been led to the invention of his hypothesis 
of a planetary explosion by the faith which astron- 
omers at that time had in Bode's Law. They ap- 
pear to have thought that several planets revolving 
in the gap where the *'law" called for but one could 
only be accounted for upon the theory that the 
original one had been broken up to form the several. 
Gravitation demanded that the remnants of a planet 
blown to pieces, no matter how their orbits might 
otherwise differ, should all return at stated periods 
to the point where the explosion had occurred ; hence 
Olbers' prediction that any asteroids that might sub- 
sequently be discovered would be found to have a 
common point of orbital intersection. And curiously 
enough all of the first asteroids found practically 
answered to this requirement. Olbers' theory seemed 
to be established. 
After the first four, no more asteroids were found 

255 



CURIOSITIES OF THE SKY 

until 1845, when one was discovered; then, in 1847, 
three more were added to the list; and after that 
searchers began to pick them up with such rapidity 
that by the close of the century hundreds were 
known, and it had become almost impossible to keep 
track of them. The first four are by far the largest 
members of the group, but their actual sizes remained 
unknown until less than twenty years ago. It was 
long supposed that Vesta was the largest, because it 
shines more brightly than any of the others; but 
finally, in 1895, Barnard, with the Lick telescope, 
definitely measured their diameters, and proved to 
everybody's surprise that Ceres is really the chief, 
and Vesta only the third in rank. His measures are 
as follows: Ceres, 477 miles; Pallas, 304 miles; 
Vesta, 239 miles; and Juno, 120 miles. They differ 
greatly in the reflective power of their surfaces, a 
fact of much significance in connection with the 
question of their origin. Vesta is, surface for surface, 
rather more than three times as brilliant as Ceres, 
whence the original mistake about its magnitude. 

Nowadays new asteroids are found frequently by 
photography, but physically they are most insignifi- 
cant bodies, their average diameter probably not ex- 
ceeding twenty miles, and some are believed not to 
exceed ten. On a planet only ten miles in diameter, 
assuming the same mean density as the earth's, 
which is undoubtedly too much, the force of gravity 
would be so slight that an average man would not 
weigh more than three ounces, and could jump off 
into space whenever he liked. 

Although the asteroids all revolve around the sun 

256 



THE RIDDLE OF THE ASTEROIDS 

in the same direction as that pursued by the major 
planets, their orbits are inclined at a great variety 
of angles to the general plane of the planetary system, 
and some of them are very eccentric — almost as much 
so as the orbits of many of the periodic comets. It 
has even been conjectured that the two tiny moons 
of Mars and the four smaller satellites of Jupiter 
may be asteroids gone astray and captured by those 
planets. Two of the asteroids are exceedingly re- 
markable for the shapes and positions of their orbits ; 
these are Eros, discovered in 1898, and T. G., 1906, 
found eight years later. The latter has a mean dis- 
tance from the sun slightly greater than that of 
Jupiter, while the mean distance of Eros is less than 
that of Mars. The orbit of Eros is so eccentric that 
at times it approaches within 15,000,000 miles of the 
earth, nearer than any other regular member of the 
solar system except the moon, thus affording an un- 
rivalled means of measuring the solar parallax. But 
for our present purpose the chief interest of Eros lies 
in its extraordinary changes of light. 

These changes, although irregular, have been ob- 
served and photographed many times, and there 
seems to be no doubt of their reality. Their signifi- 
cance consists in their possible connection with the 
form of the little planet, whose diameter is generally 
estimated at not more than twenty miles. Von 
Oppolzer found, in 1901, that Eros lost three-fourths 
of its brilliancy once in every two hours and thirty- 
eight minutes. Other observers have found slightly 
different periods of variability, but none as long as 
three hours. The most interesting interpretation 

257 



CURIOSITIES OF THE SKY 

that has been offered of this phenomenon is that it is 
due to a great irregularity of figure, recalling at once 
Gibers' hypothesis. According to some, Eros may 
be double, the two bodies composing it revolving 
around each other at very close quarters ; but a more 
striking, and it may be said probable, suggestion is 
that Eros has a form not unlike that of a dumb-bell, 
or hour-glass, turning rapidly end over end so that 
the area of illuminated surface presented to our eyes 
continually changes, reaching at certain times a 
minimum when the amount of light that it reflects 
toward the earth is reduced to a quarter of its maxi- 
mum value. Various other bizarre shapes have been 
ascribed to Eros, such, for instance, as that of a 
flat stone revolving about one of its longer axes, so 
that sometimes we see its face and sometimes its 
edge. 

All of these explanations proceed upon the as- 
sumption that Eros cannot have a simple globular 
figure like that of a typical planet, a figure which is 
prescribed by the law of gravitation, but that its 
shape is what may be called accidental; in a word, 
it is a fragment, for it seems impossible to believe that 
a body formed in interplanetary space, either through 
nebular condensation or through the aggregation of 
particles drawn together by their mutual attractions, 
should not be practically spherical in shape. Nor is 
Eros the only asteroid that gives evidence by varia- 
tions of brilliancy that there is something abnormal 
in its constitution; several others present the same 
phenomenon in varying degrees. Even Vesta was 
regarded by Gibers as sufficiently variable in its light 

258 



THE RIDDLE OF THE ASTEROIDS 

to warrant the conclusion that it was an angular mass 
instead of a globe. Some of the smaller ones show 
very notable variations, and all in short perods, of 
three or four hours, suggesting that in turning about 
one of their axes they present a surface of variable 
extent toward the sun and the earth. 

The theory which some have preferred that the 
variability of light is due to the differences of reflect- 
ive power on different parts of the surface would, 
if accepted, be hardly less suggestive of the 
origin of these little bodies by the breaking up of a 
larger one, because the most natural explanation of 
such differences would seem to be that they arose 
from variations in the roughness or smoothness of 
the reflecting surface, which would be characteristic 
of fragmentary bodies. In the case of a large planet 
alternating expanses of land and water, or of vegeta- 
tion and desert, would produce a notable variation 
in the amount of reflection, but on bodies of the size 
of the asteroids neither water nor vegetation could 
exist, and an atmosphere would be equally im- 
possible. 

One of the strongest objections to Olbers* hypoth- 
esis is that only a few of the first asteroids discovered 
travel in orbits which measurably satisfy the re- 
quirement that they should all intersect at the point 
where the explosion occurred. To this it was at first 
replied that the perturbations of the asteroidal orbits, 
by the attractions of the major planets, would soon 
displace them in such a manner that they would 
cease to intersect. One of the first investigations 
undertaken by the late Prof. Simon Newcomb was 

259 



CURIOSITIES OF THE SKY 

directed to the solution of this question, and he ar- 
rived at the conclusion that the planetary perturba- 
tions could not explain the actual situation of the 
asteroidal orbits. But afterward it was pointed out 
that the difficulty could be avoided by supposing 
that not one but a series of explosions had produced 
the asteroids as they now are. After the primary 
disruption the fragments themselves, according to 
this suggestion, may have exploded, and then the 
resulting orbits would be as "tangled" as the heart 
could wish. This has so far rehabilitated the 
explosion theory that it has never been entirely 
abandoned, and the evidence which we have just 
cited of the probably abnormal shapes of Eros and 
other asteroids has lately given it renewed life. It 
is a subject that needs a thorough rediscussion. 

We must not fail to mention, however, that there 
is a rival hypothesis which commends itself to many 
astronomers — viz., that the asteroids were formed out 
of a relatively scant ring of matter, situated between 
Mars and Jupiter and resembling in composition the 
immensely more massive rings from which, according 
to Laplace's hypothesis, the planets were born. It 
is held by the supporters of this theory that the at- 
traction of the giant Jupiter was sufficient to prevent 
the small, nebulous ring that gave birth to the 
asteroids from condensing like the others into a single 
planet. 

But if we accept the explosion theory, with its cor- 
ollary that minor explosions followed the principal 
one, we have still an unanswered question before us: 
What caused the explosions? The idea of a world 

260 



THE RIDDLE OF THE ASTEROIDS 

blowing up is too Titanic to be shocking; it rather 
amuses the imagination than seriously impresses it; 
in a word, it seems essentially chimerical. We can by 
no appeal to experience form a mental picture of 
such an occurrence. Even the moon did not blow 
up when it was wrecked by volcanoes. The ex- 
plosive nebulae and new stars are far away in space, 
and suggest no connection with such a catastrophe 
as the bursting of a planet into hundreds of pieces. 
We cannot conceive of a great globe thousands of 
miles in diameter resembling a pellet of gunpowder 
only awaiting the touch of a match to cause its sud- 
den disruption. Somehow the thought of human 
agency obtrudes itself in connection with the word 
*' explosion," and we smile at the idea that giant 
powder or nitro-glycerine could blow up a planet. 
Yet it would only need enough of them to do it. 

After all, we may deceive ourselves in thinking, as 
we are apt to do, that explosive energies lock them- 
selves up only in small masses of matter. There are 
many causes producing explosions in nature; every 
volcanic eruption manifests the activity of some of 
them. Think of the giant power of confined steam; 
if enough steam could be suddenly generated in the 
centre of the earth by a downpour of all the waters 
of the oceans, what might not the consequences be 
for our globe? In a smaller globe, and it has never 
been estimated that the original asteroid was even 
as large as the moon, such a catastrophe would, per- 
haps, be more easily conceivable; but since we are 
compelled in this case to assume that there was a 
series of successive explosions, steam would hardly 

261 



CURIOSITIES OF THE SKY 

answer the purpose; it would be more reasonable 
to suppose that the cause of the explosion was some 
kind of chemical reaction, or something affecting the 
atoms composing the exploding body. Here Dr. 
Gustav Le Bon comes to our aid with a most startling 
suggestion, based on his theory of the dissipation of 
intra-atomic energy. It will be best to quote him 
at some length from his book on The Evolution of 
Forces. 

"It does not seem at first sight," says Doctor Le 
Bon, "very comprehensible that worlds which ap- 
pear more and more stable as they cool could become 
so unstable as to afterward dissociate entirely. To 
explain this phenomenon, we will inquire whether 
astronomical observations do not allow us to witness 
this dissociation. 

"We know that the stability of a body in motion, 
such as a top or a bicycle, ceases to be possible when 
its velocity of rotation descends below a certain 
limit. Once this limit is reached it loses its stability 
and falls to the ground. Prof. J. J. Thomson even 
interprets radio-activity in this manner, and points 
out that when the speed of the elements composing 
the atoms descends below a certain limit they be- 
come unstable and tend to lose their equilibria. 
There would result from this a commencement of 
dissociation, with diminution of their potential energy 
and a corresponding increase of their kinetic energy 
sufficient to launch into space the products of intra- 
atomic disintegration. 

"It must not be forgotten that the atom being an 
enormous reservoir of energy is by this very fact 

262 



THE RIDDLE OF THE ASTEROIDS 

comparable with explosive bodies. These last re- 
main inert so long as their internal equilibria are 
undisturbed. So soon as some cause or other modi- 
fies these, they explode and smash everything around 
them after being themselves broken to pieces. 

"Atoms, therefore, which grow old in consequence 
of the diminution of a part of their intra-atomic 
energy gradually lose their stability. A moment, 
then, arrives when this stability is so weak that the 
matter disappears by a sort of explosion more or less 
rapid. The bodies of the radium group offer an 
image of this phenomenon — a rather faint image, how- 
ever, because the atoms of this body have only 
reached a period of instability when the dissociation 
is rather slow. It probably precedes another and 
more rapid period of dissociation capable of produc- 
ing their final explosion. Bodies such as radium, 
thorium, etc., represent, no doubt, a state of old age 
at which all bodies must some day arrive, and which 
they already begin to manifest in our universe, since 
all matter is slightly radio-active. It would suffice 
for the dissociation to be fairly general and fairly 
rapid for an explosion to occur in a world where it 
was manifested. 

*' These theoretical considerations find a solid sup- 
port in the sudden appearances and disappearances 
of stars. The explosions of a world which produce 
them reveal to us, perhaps, how the universes perish 
when they become old. 

**As astronomical observations show the relative 
frequency of these rapid destructions, we may ask 
ourselves whether the end of a universe by a sudden 

263 



CURIOSITIES OF THE SKY 

explosion after a long period of old age does not 
represent its most general ending." 

Here, perhaps, it will be well to stop, since, entran- 
cing as the subject may be, we know very little about 
it, and Doctor Le Bon's theory affords a limitless 
field for the reader's imagination. 



INDEX 



Aeorlites, study of, 197. 
Alcor, 58, 59. 
Alcyone, 37, 41, 42. 
Aldebaran, 62, 86. 
Alioth, 58, 59, 60. 
Alpha Centauri, 46, 66. 
Alpha Herculis, 86. 
Alnilam, 64. 
Alnita, 64. 
Anderson, Rev. Doctor, 

covers Nova Persei, 75. 
Andromeda Nebula, 75, 91 

100, 103, 104, 192. 
Antares, 86. 

Arcturus, 8, 44, 46, 66, 68. 
Arrhenius, Svante, theory, 

142, 143, 154, 158, 160, 
Aso San, crater, 219. 
Asteroids, the, 29, 252. 
Atlas, 37. 
Auriga, 75. 
Aurora Australis, 148. 
Aurora Borealis, 147, 148, 

157, 160. 

Baily, Francis, quoted, 

118. 
Belt, Orion's, 64. 
Benetnasch, 58, 59, 60. 
Betelgeuse, 64, 86. 
Biela's comet, 180, 191, 

195- 
Brooks' comet, 176, 181. 

" Black stone," the, 196. 

Bode's Law, 254, 255. 

Bredichin, researches, 184. 



dis- 



99. 



139. 
184. 



154, 



117. 



192, 



Cancer, 55. 

Canopus, 68. 

Canyon Diablo meteors, 202, 

204. 
Capella, 75, 76. 
Cassiopeia, 24, 56, 61, 69. 
Catharina, crater, 230. 
Centaurus, 14, 30. 
Ceres, 255, 256. 
Cetus, 86, 99. 
Chamberlin, Professor, theory, 

107. 
Chi Persei, 24, 
Clavius, crater, 230. 
Clerke, Agnes M., quoted, 8, 

Coal-sack, the, 2, 3, 4, 7, i^. 

Comet, Halley's, 165; Swift's, 
167; phenomena, 169; ap- 
proach to the sun, 170; of 
1811, 171; of 1882, 171, 174, 
175; their light, 171; of 1908, 
172; of 1729, 172; of 1843, 
173, 174, 175; of 1858, 173; 
of 1861, 173; of 1880, 174; 
of 1668, 175; and photog- 
raphy, 176; Brooks', 176; 
Daniels', 176; of 1770, 179; 
family, 180; Biela's, 180, 
191, 192, 195; tails, 183, 184; 
of 1744, 185; disintegration, 
191. 

Comstock, George C, theory, 
20, 33. 

Coon Butte Meteorite, 309, 204, 
211, 213, 



36s 



CURIOSITIES OF THE SKY 



Corona, 113, 144, 117, ii8, 119, 
124, 125, 130, 138. 

Coronium, 124. 

Corvus, 62. 

Craters, lunar, 216, 219-221; 
Tycho, 216, 219; Theophilus, 
219, 230; Cyrillus, 230; Catha- 
rina, 230; Longomontanus, 
230; Wilhelm I., 230; Clavius, 
230. 

Cygnus, 8, 38, 62, 73, 74. 

Cyrillus Crater, 230. 

Daniels' comet, 176, 

Delphinus, 62. 

Denning, W. F., researches, 
188. 

Diamonds in meteorites, 202. 

Donati's comet, 173, 184. 

Dubhe, 58, 59, 60. 

Dyson, Professor, investiga- 
tions, 50, 51. 

Earth, course, 47, 49; magnet, 
148, 157. 

Eclipse, of the sun, 113, 114; 
of 1842, 114, 117, 118; of 
1900, 118, 125; of 1905, 118. 

Eddington, Professor, investiga- 
tions, 50. 

Electra, 37. 

Eros, 257, 258. 

Fixed stars, 39, 40, 41. 
Forbes, Prof. George, theory, 

175- 

Galaxy, the, 2, 3, 7, 12, 13, 17, 

18, 19, 23. 
" Gegenschein," 136, 137, 142. 
Gemini, 62, 91. 
Gilbert, W. K., on lunar craters, 

221. 
Great Dipper, the, 49, 57, 58. 
Great Southern Comet, 174. 
Great Square of Pegasus, 62. 
Groombridge, 1830, motion, 

43- 



Hale, Professor, and sun- 
spots, 123. 

Halley's comet, 48, 165. 

Helium, 201. 

Hercules, 14, 25, 30, 46. 

Herschel, Alexander, and meteor 
swarms, 188. 

Herschel, Sir William, observa- 
tions, 2, 7, 26, 30, 243. 

Hyades, 22, 62. 

Hydra, 62. 

IzAMAL, temples, 54, 55. 

Janssen, Professor, theory, 

84, 85. 
Juno, 255, 256. 
Jupiter, 29, 40, 166, 179, 180 

191, 241, 

Kappa, 69. 

Kapteyn, Professor, investi- 
gations, 50. 
Keeler, Professor, discovery, 88. 
Kepler's star, 74. 

Laplace, Professor, theory, 

103, 109, III. 
Le Bon, Dr. Gustav, theory, 86; 

quoted, 260. 
Leo, 62, 187. 
Lexell's comet, 179, 180. 
Longomontanus, crater - ring, 

230. 
Lowell, Percival, observations, 

247. 
Lunar Apennines, 225. 
Lunar Caucasus, 225. 
Lyra, 88. 

Maedler, theory, 41. 
Magellanic clouds, 24. 
Magnetic storms, 126, 151, 152. 
Maia, 37. 

Mare Crismm, 235. 
Mare Imbrium, the, 235. 
Mare Serenitatis, the, 225. 
Mare Tranquilitatis, the, 229. 



266 



INDEX 



Mars, and the Asteroids, 29; 
distance from earth, 214; de- 
scription, 241, 242; habit- 
abiiity, 243; canals, 244, 247; 
resemblance to the earth, 
248; life on, 249-253. 

Maunder, E. W., quoted, 133. 

Megrez, 58, 59, 60. 

Merak, 58, 59, 60. 

Mercury, 234, 240. 

Merope, 37. 

Meteorites, study of, 197; veloc- 
ity, 198, 208; stone and iron, 
201, 202, 203; fall of, 203; 
Peary's, 208; origin, 222. 

Meteors, showers, 186, 187; 
swarms, 188; November, 191; 
of ancient times, 196; Canyon 
Diablo, 202, 204, 211. 

Milky Way, the, 2, 3, 4, 8, 9, 
12, 17, 18, 19, 20, 21, 42. 

Mintaka, 64. 

Mira Ceti, 86, 123. 

Mizar, 58, 59, 60, 

Moissan diamonds, 202. 

Moon, the, distance from earth, 
214; former conditions, 215; 
craters of, 216, 219-221; sea- 
beds, 225-229. 

Morehouse's comet, 172. 

Moulton, Professor, theory, 107. 

Nebula, Andromeda, 103, 104; 

Orion, 103, 104. 
Nebula, Trifid, 7; dark, 10, 12; 

in Orion, 30; Pleiades, 34. 
Nebula in Cetus, 10 1. 
Neptune, 241. 
Neptune, speed, 40. 
Northern Cross, 62. 
Northern Crown, 61, 63, 74, 84. 
Northern Lights, 148, 158. 
Nova Persei, 71, 75, 80, 81, 83, 

84, 85, 86. 

Olber's theory, 29, 253, 257. 
Olmstead, Prof. Denison, and 
meteors, 186, 187. 

2 



Omega Centauri, 30, 33. 

Ophiuchus, 74. 

Orion, 22, 37, 55, 63, 103, 104. 

Palladium, the, 196. 

Pallas, 255, 256. 

Perrine, discovery, 33. 

Perseus, 24, 56, 75. 

Phaed, 58, 59, 60. 

Pickering, Prof. W. H., on 

meteors, 211, 212. 
Planetesimal Hypothesis, 107, 

108, III. 
Planets, the, 39, 40, 239-241. 
Pleiades, 22, 34, 37, 49, 62. 
Pointers, the, 59. 

Rho Ophiuchi, 10. 
Rigel, 64, 86. 

Rosse, Lord, Whirlpool Nebula, 
88, 89; spiral nebulae, 92. 

Sagittarius, 4, 7. 

Saturn, 191, 241. 

Schiaparelli, discovery, 243, 244. 

Scorpio, 4, 7, 55. 

Sea of Serenity, the, 225, 226. 

Sea of Showers, the, 225. 

Sea of Tranquility, the, 229. 

Seeliger, Professor, theory, 80. 

Sickle, the, 62. 

Sirius, 44, 46, 66, 86, 202. 

Southern Cross, 3, 64, 65. 

Spiral nebulae, 112. 

Star, clouds, 23, 24, 50; swarms, 
24, 25, 50; clusters, 25-34, 
50; fixed, 39, 40 ; motions, 
43. 44. 45' 48-52; tracks, 47, 
48, 49; drift, 49. 50- 

Stars, speeding, 43, 44; tem- 
porary, 68, 69, 73, 74, 86. 

Stones, showers, 196, 197. 

Sun, eclipse, 113; surroundings, 
113; prominences, 113, 119, 
120, 124; spots, 123, 124, 127, 
151, 154, 158; a variable star, 
128. 
1 Swan, the, 4. 

67 



CURIOSITIES OF THE SKY 



Taurus, 62. 

Taygeta, 37. 

Theophilus, crater, 219, 230. 

Tidal explosion, 108. 

Tides in couples, 107. 

Triangulum, 96, 99, 100. 

Trifid Nebula, 7. 

Twins, the, 62. 

Tycho, crater, 216, 219. 

Tycho's Star, 69, 70, 71, 73. 

Uranus, 188, 241. 
Ursa Major, 57, 97, 99. 



Vega, 46, 66. 
Venus, 70, 240. 
Vesta, 255, 256, 258. 

Whirlpool Nebula, Rosse's, 88. 
Wilhelm I., crater-ring, 230. 
Wolf, Rudolph, discovery, 151. 

Young, Professor, coronium, 
124. 

Zodiacal Light, the, 131-143. 
Zurich Chronicles, ancient, 151. 



THE END 



(KM 131*» 



NOV 



\909 



